WebGL's SVGImage buffer should be cleared

Source/modules/webgl/WebGLRenderingContextBase.cpp

Index: Source/modules/webgl/WebGLRenderingContextBase.cpp
diff --git a/Source/modules/webgl/WebGLRenderingContextBase.cpp b/Source/modules/webgl/WebGLRenderingContextBase.cpp
index d343f6da8301e70e4195c4d8d9d466fd0090403d..a716ebd6d32b6ebeae47bb7171008705500e2298 100644
--- a/Source/modules/webgl/WebGLRenderingContextBase.cpp
+++ b/Source/modules/webgl/WebGLRenderingContextBase.cpp
@@ -4123,8 +4123,13 @@ bool WebGLRenderingContextBase::validateValueFitNonNegInt32(const char* function
     return true;
 }
 
-PassRefPtr<Image> WebGLRenderingContextBase::drawImageIntoBuffer(Image* image, int width, int height, const char* functionName)
+// TODO(fmalita): figure why WebGLImageConversion::ImageExtractor can't handle SVG-backed images,
+// and get rid of this intermediate step.
+PassRefPtr<Image> WebGLRenderingContextBase::drawImageIntoBuffer(PassRefPtr<Image> image, int width,
+    int height, const char* functionName)
 {
+    ASSERT(image);

[Ken Russell (switch to Gerrit), 2015/09/08 19:34:01]

If this is being changed to take PassRefPtr<Image> then please make a RefPtr for
it upon entry. Otherwise it's easy to accidentally call the copy constructor of
PassRefPtr, zeroing its internal field and causing crashes later.

[f(malita), 2015/09/08 19:51:42]

Done.

+
     IntSize size(width, height);
     ImageBuffer* buf = m_generatedImageCache.imageBuffer(size);
     if (!buf) {
@@ -4132,6 +4137,9 @@ PassRefPtr<Image> WebGLRenderingContextBase::drawImageIntoBuffer(Image* image, i
         return nullptr;
     }
 
+    if (!image->currentFrameKnownToBeOpaque())

[pdr., 2015/09/08 18:33:58]

Why wasn't this needed for transparent animated gifs where the first frame has
transparency?

[f(malita), 2015/09/08 18:44:45]

We only ever call drawImageIntoBuffer for SVG images.  All other types are
handled directly by WebGLImageConversion::ImageExtractor and don't need to go
through intermediate buffers.

+        buf->canvas()->clear(SK_ColorTRANSPARENT);
+
     IntRect srcRect(IntPoint(), image->size());
     IntRect destRect(0, 0, size.width(), size.height());
     SkPaint paint;
@@ -4197,8 +4205,8 @@ void WebGLRenderingContextBase::texImage2D(GLenum target, GLint level, GLenum in
         return;
 
     RefPtr<Image> imageForRender = image->cachedImage()->imageForLayoutObject(image->layoutObject());
-    if (imageForRender->isSVGImage())
-        imageForRender = drawImageIntoBuffer(imageForRender.get(), image->width(), image->height(), "texImage2D");
+    if (imageForRender && imageForRender->isSVGImage())
+        imageForRender = drawImageIntoBuffer(imageForRender.release(), image->width(), image->height(), "texImage2D");
 
     if (!imageForRender || !validateTexFunc("texImage2D", NotTexSubImage2D, SourceHTMLImageElement, target, level, internalformat, imageForRender->width(), imageForRender->height(), 0, format, type, 0, 0))
         return;
@@ -4507,8 +4515,8 @@ void WebGLRenderingContextBase::texSubImage2D(GLenum target, GLint level, GLint
         return;
 
     RefPtr<Image> imageForRender = image->cachedImage()->imageForLayoutObject(image->layoutObject());
-    if (imageForRender->isSVGImage())
-        imageForRender = drawImageIntoBuffer(imageForRender.get(), image->width(), image->height(), "texSubImage2D");
+    if (imageForRender && imageForRender->isSVGImage())
+        imageForRender = drawImageIntoBuffer(imageForRender.release(), image->width(), image->height(), "texSubImage2D");
 
     if (!imageForRender || !validateTexFunc("texSubImage2D", TexSubImage2D, SourceHTMLImageElement, target, level, 0, imageForRender->width(), imageForRender->height(), 0, format, type, xoffset, yoffset))
         return;