Revert "explictly fail to draw unpremul, as this is buggy, incomplete, tricky, and unused"

This reverts commit 1baaacac74d24604e3dfca9857fbd647df375997.

Reason for revert: Failing the roll: https://storage.googleapis.com/chromium-layout-test-archives/linux_trusty_blink_rel/3868/layout-test-results/results.html

Original change's description:
> explictly fail to draw unpremul, as this is buggy, incomplete, tricky, and unused
> 
> BUG=skia:
> 
> Change-Id: Ie9da6015cc4955c0f27f6db53fc6ae532e0132f4
> Reviewed-on: https://skia-review.googlesource.com/7304
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Matt Sarett <msarett@google.com>
> 

TBR=bsalomon@google.com,msarett@google.com,brianosman@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Change-Id: Ifc808a430b8afe4fef6df3775c2bfdcede1a2dd7
Reviewed-on: https://skia-review.googlesource.com/7329
Commit-Queue: Joe Gregorio <jcgregorio@google.com>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>

4 files changed, 5 insertions, 35 deletions

diff --git a/gm/all_bitmap_configs.cpp b/gm/all_bitmap_configs.cpp
index 0d9c2c5a3d..e954fc33e5 100644
--- a/gm/all_bitmap_configs.cpp
+++ b/gm/all_bitmap_configs.cpp
@@ -260,37 +260,27 @@ static void make_color_test_bitmap_variant(
             *pm.writable_addr32(x, y) = make_pixel(x, y, alphaType);
         }
     }
-    bm->setImmutable();
 }
 
-DEF_SIMPLE_GM(all_variants_8888, canvas, 4 * SCALE + 30, 4 * SCALE + 30) {
+DEF_SIMPLE_GM(all_variants_8888, canvas, 4 * SCALE + 30, 2 * SCALE + 10) {
     sk_tool_utils::draw_checkerboard(canvas, SK_ColorLTGRAY, SK_ColorWHITE, 8);
 
     sk_sp<SkColorSpace> colorSpaces[] {
         SkColorSpace::MakeNamed(SkColorSpace::kSRGB_Named),
         nullptr,
     };
-
-    SkPaint rectPaint;
-    rectPaint.setColor(0x8000FF00);
-    SkRect r = { 0, 0, SCALE, SCALE };
-
     for (auto colorSpace : colorSpaces) {
         canvas->save();
-        // unpremul is expected to *not* draw anything
         for (auto alphaType : {kPremul_SkAlphaType, kUnpremul_SkAlphaType}) {
             canvas->save();
             for (auto colorType : {kRGBA_8888_SkColorType, kBGRA_8888_SkColorType}) {
                 SkBitmap bm;
                 make_color_test_bitmap_variant(colorType, alphaType, colorSpace, &bm);
-                canvas->drawRect(r, rectPaint);
                 canvas->drawBitmap(bm, 0.0f, 0.0f);
-                canvas->drawRect(r.makeOffset(0, SCALE + 10), rectPaint);
-                canvas->drawImage(SkImage::MakeFromBitmap(bm), 0, SCALE + 10, nullptr);
                 canvas->translate(SCALE + 10, 0.0f);
             }
             canvas->restore();
-            canvas->translate(0.0f, (SCALE + 10) * 2);
+            canvas->translate(0.0f, SCALE + 10);
         }
         canvas->restore();
         canvas->translate(2 * (SCALE + 10), 0.0f);
diff --git a/include/core/SkImageInfo.h b/include/core/SkImageInfo.h
index 2dea479c6f..4a8c2860fc 100644
--- a/include/core/SkImageInfo.h
+++ b/include/core/SkImageInfo.h
@@ -40,8 +40,8 @@ enum SkAlphaType {
      *  All pixels have their color components stored without any regard to the
      *  alpha. e.g. this is the default configuration for PNG images.
      *
-     *  This alpha-type is ONLY supported for readPixels/writePixels operations,
-     *  and is not supported for drawing.
+     *  This alpha-type is ONLY supported for input images. Rendering cannot
+     *  generate this on output.
      */
     kUnpremul_SkAlphaType,
 
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 367a348f51..0375ab738d 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -53,12 +53,6 @@
 
 #define RETURN_ON_NULL(ptr)     do { if (nullptr == (ptr)) return; } while (0)
 
-#define RETURN_ON_UNPREMUL_IMAGE(image) \
-    do { if (as_IB(image)->onAlphaType() == kUnpremul_SkAlphaType) return; } while (0)
-
-#define RETURN_ON_UNPREMUL_BITMAP(bitmap) \
-    do { if (bitmap.alphaType() == kUnpremul_SkAlphaType) return; } while (0)
-
 /*
  *  Return true if the drawing this rect would hit every pixels in the canvas.
  *
@@ -1915,14 +1909,12 @@ void SkCanvas::drawPath(const SkPath& path, const SkPaint& paint) {
 
 void SkCanvas::drawImage(const SkImage* image, SkScalar x, SkScalar y, const SkPaint* paint) {
     RETURN_ON_NULL(image);
-    RETURN_ON_UNPREMUL_IMAGE(image);
     this->onDrawImage(image, x, y, paint);
 }
 
 void SkCanvas::drawImageRect(const SkImage* image, const SkRect& src, const SkRect& dst,
                              const SkPaint* paint, SrcRectConstraint constraint) {
     RETURN_ON_NULL(image);
-    RETURN_ON_UNPREMUL_IMAGE(image);
     if (dst.isEmpty() || src.isEmpty()) {
         return;
     }
@@ -1932,14 +1924,12 @@ void SkCanvas::drawImageRect(const SkImage* image, const SkRect& src, const SkRe
 void SkCanvas::drawImageRect(const SkImage* image, const SkIRect& isrc, const SkRect& dst,
                              const SkPaint* paint, SrcRectConstraint constraint) {
     RETURN_ON_NULL(image);
-    RETURN_ON_UNPREMUL_IMAGE(image);
     this->drawImageRect(image, SkRect::Make(isrc), dst, paint, constraint);
 }
 
 void SkCanvas::drawImageRect(const SkImage* image, const SkRect& dst, const SkPaint* paint,
                              SrcRectConstraint constraint) {
     RETURN_ON_NULL(image);
-    RETURN_ON_UNPREMUL_IMAGE(image);
     this->drawImageRect(image, SkRect::MakeIWH(image->width(), image->height()), dst, paint,
                         constraint);
 }
@@ -1947,7 +1937,6 @@ void SkCanvas::drawImageRect(const SkImage* image, const SkRect& dst, const SkPa
 void SkCanvas::drawImageNine(const SkImage* image, const SkIRect& center, const SkRect& dst,
                              const SkPaint* paint) {
     RETURN_ON_NULL(image);
-    RETURN_ON_UNPREMUL_IMAGE(image);
     if (dst.isEmpty()) {
         return;
     }
@@ -1961,7 +1950,6 @@ void SkCanvas::drawImageNine(const SkImage* image, const SkIRect& center, const
 void SkCanvas::drawImageLattice(const SkImage* image, const Lattice& lattice, const SkRect& dst,
                                 const SkPaint* paint) {
     RETURN_ON_NULL(image);
-    RETURN_ON_UNPREMUL_IMAGE(image);
     if (dst.isEmpty()) {
         return;
     }
@@ -1984,7 +1972,6 @@ void SkCanvas::drawBitmap(const SkBitmap& bitmap, SkScalar dx, SkScalar dy, cons
     if (bitmap.drawsNothing()) {
         return;
     }
-    RETURN_ON_UNPREMUL_BITMAP(bitmap);
     this->onDrawBitmap(bitmap, dx, dy, paint);
 }
 
@@ -1993,7 +1980,6 @@ void SkCanvas::drawBitmapRect(const SkBitmap& bitmap, const SkRect& src, const S
     if (bitmap.drawsNothing() || dst.isEmpty() || src.isEmpty()) {
         return;
     }
-    RETURN_ON_UNPREMUL_BITMAP(bitmap);
     this->onDrawBitmapRect(bitmap, &src, dst, paint, constraint);
 }
 
@@ -2013,7 +1999,6 @@ void SkCanvas::drawBitmapNine(const SkBitmap& bitmap, const SkIRect& center, con
     if (bitmap.drawsNothing() || dst.isEmpty()) {
         return;
     }
-    RETURN_ON_UNPREMUL_BITMAP(bitmap);
     if (SkLatticeIter::Valid(bitmap.width(), bitmap.height(), center)) {
         this->onDrawBitmapNine(bitmap, center, dst, paint);
     } else {
@@ -2026,7 +2011,6 @@ void SkCanvas::drawBitmapLattice(const SkBitmap& bitmap, const Lattice& lattice,
     if (bitmap.drawsNothing() || dst.isEmpty()) {
         return;
     }
-    RETURN_ON_UNPREMUL_BITMAP(bitmap);
 
     SkIRect bounds;
     Lattice latticePlusBounds = lattice;
@@ -2046,10 +2030,10 @@ void SkCanvas::drawAtlas(const SkImage* atlas, const SkRSXform xform[], const Sk
                          const SkColor colors[], int count, SkBlendMode mode,
                          const SkRect* cull, const SkPaint* paint) {
     RETURN_ON_NULL(atlas);
-    RETURN_ON_UNPREMUL_IMAGE(atlas);
     if (count <= 0) {
         return;
     }
+    SkASSERT(atlas);
     SkASSERT(tex);
     this->onDrawAtlas(atlas, xform, tex, colors, count, mode, cull, paint);
 }
diff --git a/src/image/SkImageShader.cpp b/src/image/SkImageShader.cpp
index 5cb1c24c5a..5b79fb1d9e 100644
--- a/src/image/SkImageShader.cpp
+++ b/src/image/SkImageShader.cpp
@@ -103,10 +103,6 @@ static bool bitmap_is_too_big(int w, int h) {
 sk_sp<SkShader> SkImageShader::Make(sk_sp<SkImage> image, TileMode tx, TileMode ty,
                                     const SkMatrix* localMatrix,
                                     SkTBlitterAllocator* allocator) {
-    if (image && as_IB(image)->onAlphaType() == kUnpremul_SkAlphaType) {
-        return nullptr;
-    }
-
     SkShader* shader;
     if (!image || bitmap_is_too_big(image->width(), image->height())) {
         if (nullptr == allocator) {