Revert of remove unused SkCachingPixelRef (patchset #1 id:1 of https://codereview.chromium.org/1364743002/ )

Reason for revert:
Build failure: https://uberchromegw.corp.google.com/i/client.skia.compile/builders/Build-Ubuntu-GCC-Arm7-Debug-Android_FrameworkDefs/builds/1146

Original issue's description:
> remove unused SkCachingPixelRef
>
> BUG=skia:
> TBR=
>
> Committed: https://skia.googlesource.com/skia/+/70d58b7da535e32bcac35739d11ab8367e99f224

TBR=halcanary@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1359393004

2 files changed, 141 insertions, 0 deletions

diff --git a/src/lazy/SkCachingPixelRef.cpp b/src/lazy/SkCachingPixelRef.cpp
new file mode 100644
index 0000000000..692e4ea3d6
--- /dev/null
+++ b/src/lazy/SkCachingPixelRef.cpp
@@ -0,0 +1,74 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCachingPixelRef.h"
+#include "SkBitmapCache.h"
+#include "SkRect.h"
+
+bool SkCachingPixelRef::Install(SkImageGenerator* generator,
+                                SkBitmap* dst) {
+    SkASSERT(dst != nullptr);
+    if (nullptr == generator) {
+        return false;
+    }
+    const SkImageInfo info = generator->getInfo();
+    if (!dst->setInfo(info)) {
+        delete generator;
+        return false;
+    }
+    SkAutoTUnref<SkCachingPixelRef> ref(new SkCachingPixelRef(info, generator, dst->rowBytes()));
+    dst->setPixelRef(ref);
+    return true;
+}
+
+SkCachingPixelRef::SkCachingPixelRef(const SkImageInfo& info,
+                                     SkImageGenerator* generator,
+                                     size_t rowBytes)
+    : INHERITED(info)
+    , fImageGenerator(generator)
+    , fErrorInDecoding(false)
+    , fRowBytes(rowBytes) {
+    SkASSERT(fImageGenerator != nullptr);
+}
+SkCachingPixelRef::~SkCachingPixelRef() {
+    delete fImageGenerator;
+    // Assert always unlock before unref.
+}
+
+bool SkCachingPixelRef::onNewLockPixels(LockRec* rec) {
+    if (fErrorInDecoding) {
+        return false;  // don't try again.
+    }
+
+    const SkImageInfo& info = this->info();
+    if (!SkBitmapCache::Find(
+                this->getGenerationID(), info.bounds(), &fLockedBitmap)) {
+        // Cache has been purged, must re-decode.
+        if (!fLockedBitmap.tryAllocPixels(info, fRowBytes)) {
+            fErrorInDecoding = true;
+            return false;
+        }
+        if (!fImageGenerator->getPixels(info, fLockedBitmap.getPixels(), fRowBytes)) {
+            fErrorInDecoding = true;
+            return false;
+        }
+        fLockedBitmap.setImmutable();
+        SkBitmapCache::Add(this, info.bounds(), fLockedBitmap);
+    }
+
+    // Now bitmap should contain a concrete PixelRef of the decoded image.
+    void* pixels = fLockedBitmap.getPixels();
+    SkASSERT(pixels != nullptr);
+    rec->fPixels = pixels;
+    rec->fColorTable = nullptr;
+    rec->fRowBytes = fLockedBitmap.rowBytes();
+    return true;
+}
+
+void SkCachingPixelRef::onUnlockPixels() {
+    fLockedBitmap.reset();
+}
diff --git a/src/lazy/SkCachingPixelRef.h b/src/lazy/SkCachingPixelRef.h
new file mode 100644
index 0000000000..1057441d5e
--- /dev/null
+++ b/src/lazy/SkCachingPixelRef.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCachingPixelRef_DEFINED
+#define SkCachingPixelRef_DEFINED
+
+#include "SkBitmapCache.h"
+#include "SkImageInfo.h"
+#include "SkImageGenerator.h"
+#include "SkPixelRef.h"
+
+class SkColorTable;
+
+/**
+ *  PixelRef which defers decoding until SkBitmap::lockPixels() is
+ *  called.  Caches the decoded images in the global
+ *  SkScaledImageCache.  When the pixels are unlocked, this cache may
+ *  or be destroyed before the next lock.  If so, onLockPixels will
+ *  attempt to re-decode.
+ *
+ *  Decoding is handled by the SkImageGenerator
+ */
+class SkCachingPixelRef : public SkPixelRef {
+public:
+    
+    /**
+     *  Takes ownership of SkImageGenerator.  If this method fails for
+     *  whatever reason, it will return false and immediatetely delete
+     *  the generator.  If it succeeds, it will modify destination
+     *  bitmap.
+     *
+     *  If Install fails or when the SkCachingPixelRef that is
+     *  installed into destination is destroyed, it will call
+     *  `delete` on the generator.  Therefore, generator should be
+     *  allocated with `new`.
+     */
+    static bool Install(SkImageGenerator* gen, SkBitmap* dst);
+
+protected:
+    virtual ~SkCachingPixelRef();
+    bool onNewLockPixels(LockRec*) override;
+    void onUnlockPixels() override;
+    bool onLockPixelsAreWritable() const override { return false; }
+
+    SkData* onRefEncodedData() override {
+        return fImageGenerator->refEncodedData();
+    }
+
+    bool onIsLazyGenerated() const override { return true; }
+
+private:
+    SkImageGenerator* const fImageGenerator;
+    bool                    fErrorInDecoding;
+    const size_t            fRowBytes;
+
+    SkBitmap                fLockedBitmap;
+
+    SkCachingPixelRef(const SkImageInfo&, SkImageGenerator*, size_t rowBytes);
+
+    typedef SkPixelRef INHERITED;
+};
+
+#endif  // SkCachingPixelRef_DEFINED