Revert "Redefine the meaning of sample counts in GPU backend."

This reverts commit 48825b11ad25c98b9a4884d5cc0edd4e290c4409.

Reason for revert: nanobench

Original change's description:
> Redefine the meaning of sample counts in GPU backend.
> 
> Old: 0  -> nonMSAA
>      1+ -> MSAA
> 
> New:
>      0  -> error/unsupported
>      1  -> nonMSAA
>      2+ -> MSAA
> 
> We still allow 0 to mean nonMSAA in three sets of public APIs for backwards compatibility:
> 
> 1) SkSurface factories
> 2) GrBackendRenderTarget constructors
> 3) GrCaps::getSampleCnt()'s requestedCount parameter
> 
> However, we immediately clamp to 1 and treat 0 as invalid/non-renderable internally.
> 
> This also changes the behavior when using a large sample count. We now fail in that case rather than using the largest sample available sample count. GrCaps::getSampleCount() will return 0 in this case.
> 
> 
> Bug: skia:
> Change-Id: Ida22c6b22c1365e563c9046b611e88bf5eb3ff33
> Reviewed-on: https://skia-review.googlesource.com/101560
> Reviewed-by: Greg Daniel <egdaniel@google.com>
> Commit-Queue: Brian Salomon <bsalomon@google.com>

TBR=egdaniel@google.com,bsalomon@google.com

Change-Id: Ic257619a8a5ee9ac15419ecf10259e42daed7f82
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/102662
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

2 files changed, 4 insertions, 11 deletions

diff --git a/src/utils/win/SkWGL.h b/src/utils/win/SkWGL.h
index cd19f2eeba..c6c9479abe 100644
--- a/src/utils/win/SkWGL.h
+++ b/src/utils/win/SkWGL.h
@@ -83,8 +83,7 @@ public:
      * priority are:
      *     * Choose formats with the smallest sample count that is >=
      *       desiredSampleCount (or the largest sample count if all formats have
-     *       fewer samples than desiredSampleCount.) If desiredSampleCount is 1 then
-     *       all msaa formats are excluded from consideration.
+     *       fewer samples than desiredSampleCount.)
      *     * Choose formats with the fewest color samples when coverage sampling
      *       is available.
      *     * If the above rules leave multiple formats, choose the one that
@@ -131,9 +130,8 @@ enum SkWGLContextRequest {
 /**
  * Helper to create an OpenGL context for a DC using WGL. Configs with a sample count >= to
  * msaaSampleCount are preferred but if none is available then a context with a lower sample count
- * (including non-MSAA) will be created. If msaaSampleCount is 1 then this will fail if a non-msaa
- * context cannot be created. If preferCoreProfile is true but a core profile cannot be created
- * then a compatible profile context will be created.
+ * (including non-MSAA) will be created. If preferCoreProfile is true but a core profile cannot be
+ * created then a compatible profile context will be created.
  */
 HGLRC SkCreateWGLContext(HDC dc, int msaaSampleCount, bool deepColor, SkWGLContextRequest context,
                          HGLRC shareContext = nullptr);
diff --git a/src/utils/win/SkWGL_win.cpp b/src/utils/win/SkWGL_win.cpp
index 441d7a4ebb..b7c89944e0 100644
--- a/src/utils/win/SkWGL_win.cpp
+++ b/src/utils/win/SkWGL_win.cpp
@@ -126,7 +126,6 @@ int SkWGLExtensions::selectFormat(const int formats[],
                                   int formatCount,
                                   HDC dc,
                                   int desiredSampleCount) const {
-    SkASSERT(desiredSampleCount >= 1);
     if (formatCount <= 0) {
         return -1;
     }
@@ -147,7 +146,7 @@ int SkWGLExtensions::selectFormat(const int formats[],
                                      &kQueryAttr,
                                      &numSamples);
         rankedFormats[i].fFormat =  formats[i];
-        rankedFormats[i].fSampleCnt = SkTMax(1, numSamples);
+        rankedFormats[i].fSampleCnt = numSamples;
         rankedFormats[i].fChoosePixelFormatRank = i;
     }
     SkTQSort(rankedFormats.begin(),
@@ -160,10 +159,6 @@ int SkWGLExtensions::selectFormat(const int formats[],
     if (idx < 0) {
         idx = ~idx;
     }
-    // If the caller asked for non-MSAA fail if the closest format has MSAA.
-    if (desiredSampleCount == 1 && rankedFormats[idx].fSampleCnt != 1) {
-        return -1;
-    }
     return rankedFormats[idx].fFormat;
 }