DeferredImageDecoder: early-out onGetYUV8Planes when possible

third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp

Index: third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp b/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
index cd34b54fce2c9e1f6bd72e18027b61b6d1c28352..1470a16d38182e6cf04c54c6647dfd62c972dd49 100644
--- a/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
+++ b/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
@@ -27,7 +27,6 @@
 #include "platform/graphics/DecodingImageGenerator.h"
 
 #include "platform/PlatformInstrumentation.h"
-#include "platform/RuntimeEnabledFeatures.h"
 #include "platform/SharedBuffer.h"
 #include "platform/TraceEvent.h"
 #include "platform/graphics/ImageFrameGenerator.h"
@@ -41,6 +40,7 @@ DecodingImageGenerator::DecodingImageGenerator(PassRefPtr<ImageFrameGenerator> f
     , m_frameGenerator(frameGenerator)
     , m_frameIndex(index)
     , m_generationId(0)
+    , m_canYUVDecode(false)
 {
 }
 
@@ -63,8 +63,7 @@ SkData* DecodingImageGenerator::onRefEncodedData()
     return 0;
 }
 
-bool DecodingImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
-    SkPMColor ctable[], int* ctableCount)
+bool DecodingImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, SkPMColor table[], int* tableCount)
 {
     TRACE_EVENT1("blink", "DecodingImageGenerator::getPixels", "frame index", static_cast<int>(m_frameIndex));
 
@@ -73,8 +72,8 @@ bool DecodingImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels,
         return false;
 
     if (info.colorType() != getInfo().colorType()) {
-        // ImageFrame may have changed the owning SkBitmap to kOpaque_SkAlphaType after sniffing the encoded data, so if we see a request
-        // for opaque, that is ok even if our initial alphatype was not opaque.
+        // blink::ImageFrame may have changed the owning SkBitmap to kOpaque_SkAlphaType after fully decoding the image frame,
+        // so if we see a request for opaque, that is ok even if our initial alpha type was not opaque.
         return false;

[Noel Gordon, 2015/12/08 01:48:10]

Tried to correct this comment for what blink::ImageFrame actually does.

Even given the comment, it is a confusing one: the code returns false here!  I
suppose the system is not broken, but I'm not really sure what this comment is
trying to say.

[scroggo, 2015/12/08 15:11:28]

It's trying to explain why we check that the color type matches (and return
false if it does not), but we do not check for the alpha type (so the alpha type
may not match).

     }
 
@@ -87,7 +86,7 @@ bool DecodingImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels,
 
 bool DecodingImageGenerator::onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3], SkYUVColorSpace* colorSpace)
 {
-    if (!RuntimeEnabledFeatures::decodeToYUVEnabled())
+    if (!m_canYUVDecode)
         return false;
 
     bool requestingYUVSizes = !planes || !planes[0];
@@ -97,11 +96,12 @@ bool DecodingImageGenerator::onGetYUV8Planes(SkISize sizes[3], void* planes[3],
     if (requestingYUVSizes)
         return m_frameGenerator->getYUVComponentSizes(sizes);
 
+    if (colorSpace)
+        *colorSpace = kJPEG_SkYUVColorSpace;
+
     PlatformInstrumentation::willDecodeLazyPixelRef(m_generationId);
     bool decoded = m_frameGenerator->decodeToYUV(sizes, planes, rowBytes);
     PlatformInstrumentation::didDecodeLazyPixelRef();
-    if (colorSpace)
-        *colorSpace = kJPEG_SkYUVColorSpace;
 
     return decoded;
 }