Determine if OffscreenCanvas is paintable in different rendering contexts

third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h

Index: third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h
diff --git a/third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h b/third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h
index e4282bba4dbd6a9a87b3b495790cc404410bc392..4ec6dfbad3b246e2000c809f4c2bfd6dc9c9cc19 100644
--- a/third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h
+++ b/third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h
@@ -48,6 +48,16 @@ namespace blink {
 
 class GraphicsContext;
 
+/**** constants ****/
+
+// Firefox limits width/height to 32767 pixels, but slows down dramatically before it
+// reaches that limit. We limit by area instead, giving us larger maximum dimensions,
+// in exchange for a smaller maximum canvas size.
+const int PLATFORM_EXPORT MaxCanvasArea = 32768 * 8192; // Maximum canvas area in CSS pixels

[Justin Novosad, 2016/08/19 17:30:01]

Defining a const in a header can lead to symbol clashes, we use "extern" to
avois this.  But that is moot anyways: the style guide encourages the use of
enums for integer constants.  And we now us a "k" prefix.  Just use an anonymous
enum, like this.

enum {
    kMaxCanvasArea = 32768 * 8192,
    kMaxSkiaDim = 32767
}

[xlai (Olivia), 2016/08/19 17:42:03]

Done.

+
+// In Skia, we will also limit width/height to 32767.
+const int PLATFORM_EXPORT MaxSkiaDim = 32767; // Maximum width/height in CSS pixels.
+
 SkXfermode::Mode PLATFORM_EXPORT WebCoreCompositeToSkiaComposite(CompositeOperator, WebBlendMode = WebBlendModeNormal);
 CompositeOperator PLATFORM_EXPORT compositeOperatorFromSkia(SkXfermode::Mode);
 WebBlendMode PLATFORM_EXPORT blendModeFromSkia(SkXfermode::Mode);