Fix crash when allocation of very large HTML canvas fails.

This change introduces skia::TryCreateBitmapCanvas, which is a 
non-crashing version of CreateBitmapCanvas.  This patch alone
does not fix that crash. A patch in WebKit will be necessary
to make the ImageBuffer constructor in ImageBufferSkia.cpp
call TryCreateBitmapCanvas.

BUG=88038
TEST=http://www.atopon.org/maze/
Review URL: http://codereview.chromium.org/7686006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@97474 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 16 insertions, 0 deletions

diff --git a/skia/ext/platform_canvas.cc b/skia/ext/platform_canvas.cc
index df7ded6..279af45 100644
--- a/skia/ext/platform_canvas.cc
+++ b/skia/ext/platform_canvas.cc
@@ -34,6 +34,15 @@ SkCanvas* CreateBitmapCanvas(int width, int height, bool is_opaque) {
   return new PlatformCanvas(width, height, is_opaque);
 }
 
+SkCanvas* TryCreateBitmapCanvas(int width, int height, bool is_opaque) {
+  PlatformCanvas* canvas = new PlatformCanvas();
+  if (!canvas->initialize(width, height, is_opaque)) {
+    delete canvas;
+    canvas = NULL;
+  }
+  return canvas;
+}
+
 SkDevice* GetTopDevice(const SkCanvas& canvas) {
   SkCanvas::LayerIter iter(const_cast<SkCanvas*>(&canvas), false);
   return iter.device();
diff --git a/skia/ext/platform_canvas.h b/skia/ext/platform_canvas.h
index 54650ff..354314b 100644
--- a/skia/ext/platform_canvas.h
+++ b/skia/ext/platform_canvas.h
@@ -109,6 +109,13 @@ SK_API SkDevice* GetTopDevice(const SkCanvas& canvas);
 // transparency: this will enable some optimizations.
 SK_API SkCanvas* CreateBitmapCanvas(int width, int height, bool is_opaque);
 
+// Non-crashing version of CreateBitmapCanvas
+// returns NULL if allocation fails for any reason.
+// Use this instead of CreateBitmapCanvas in places that are likely to
+// attempt to allocate very large canvases (therefore likely to fail),
+// and where it is possible to recover gracefully from the failed allocation.
+SK_API SkCanvas* TryCreateBitmapCanvas(int width, int height, bool is_opaque);
+
 // Returns true if native platform routines can be used to draw on the
 // given canvas. If this function returns false, BeginPlatformPaint will
 // return NULL PlatformSurface.