Optionally clear PlatformCanvas instances.

skia/ext/platform_canvas.h

Index: skia/ext/platform_canvas.h
===================================================================
--- skia/ext/platform_canvas.h	(revision 123041)
+++ skia/ext/platform_canvas.h	(working copy)
@@ -20,25 +20,25 @@
  public:
   // If you use the version with no arguments, you MUST call initialize()
   PlatformCanvas();
-  // Set is_opaque if you are going to erase the bitmap and not use
+  // Set flags to FLAGS_OPAQUE  if you are going to erase the bitmap and not use
   // transparency: this will enable some optimizations.
-  PlatformCanvas(int width, int height, bool is_opaque);
+  // Set flags to FLAGS_INITIALIZED if the canvas should be initialized to 0.
+  PlatformCanvas(int width, int height, int flags);
 
 #if defined(WIN32)
   // The shared_section parameter is passed to gfx::PlatformDevice::create.
   // See it for details.
-  PlatformCanvas(int width, int height, bool is_opaque, HANDLE shared_section);
+  PlatformCanvas(int width, int height, int flags, HANDLE shared_section);
 #elif defined(__APPLE__)
-  PlatformCanvas(int width, int height, bool is_opaque,
-                 CGContextRef context);
-  PlatformCanvas(int width, int height, bool is_opaque, uint8_t* context);
+  PlatformCanvas(int width, int height, int flags, CGContextRef context);
+  PlatformCanvas(int width, int height, int flags, uint8_t* context);
 #elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
       defined(__sun) || defined(ANDROID)
   // Linux ---------------------------------------------------------------------
 
   // Construct a canvas from the given memory region. The memory is not cleared
   // first. @data must be, at least, @height * StrideForWidth(@width) bytes.
-  PlatformCanvas(int width, int height, bool is_opaque, uint8_t* data);
+  PlatformCanvas(int width, int height, int flags, uint8_t* data);
 #endif
 
   virtual ~PlatformCanvas();
@@ -47,17 +47,17 @@
   // For two-part init, call if you use the no-argument constructor above. Note
   // that we want this to optionally match the Linux initialize if you only
   // pass 3 arguments, hence the evil default argument.
-  bool initialize(int width, int height, bool is_opaque,
+  bool initialize(int width, int height, int flags,
                   HANDLE shared_section = NULL);
 #elif defined(__APPLE__)
   // For two-part init, call if you use the no-argument constructor above
-  bool initialize(CGContextRef context, int width, int height, bool is_opaque);
-  bool initialize(int width, int height, bool is_opaque, uint8_t* data = NULL);
+  bool initialize(CGContextRef context, int width, int height, int flags);
+  bool initialize(int width, int height, int flags, uint8_t* data = NULL);
 
 #elif defined(__linux__) || defined(__FreeBSD__) || defined(__OpenBSD__) || \
       defined(__sun) || defined(ANDROID)
   // For two-part init, call if you use the no-argument constructor above
-  bool initialize(int width, int height, bool is_opaque, uint8_t* data = NULL);
+  bool initialize(int width, int height, int flags, uint8_t* data = NULL);
 #endif
 
   // Shared --------------------------------------------------------------------
@@ -109,12 +109,19 @@
 // transparency: this will enable some optimizations.
 SK_API SkCanvas* CreateBitmapCanvas(int width, int height, bool is_opaque);
 
+// Creates a canvas with raster bitmap backing.
+// Set flags to FLAGS_OPAQUE  if you are going to erase the bitmap and not use
+// transparency: this will enable some optimizations.
+// Set flags to FLAGS_INITIALIZED if the canvas should be initialized to 0.
+SK_API SkCanvas* CreateBitmapCanvas(int width, int height, int flags);
+
 // 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);
+SK_API SkCanvas* TryCreateBitmapCanvas(int width, int height, int flags);
 
 // Returns true if native platform routines can be used to draw on the
 // given canvas. If this function returns false, BeginPlatformPaint will