Optionally clear PlatformCanvas instances.

skia/ext/bitmap_platform_device_android.cc

Index: skia/ext/bitmap_platform_device_android.cc
===================================================================
--- skia/ext/bitmap_platform_device_android.cc	(revision 127021)
+++ skia/ext/bitmap_platform_device_android.cc	(working copy)
@@ -21,21 +21,25 @@
   return NULL;
 }
 
+BitmapPlatformDevice* BitmapPlatformDevice::CreateAndClear(int width,
+                                                           int height,
+                                                           bool is_opaque) {
+  BitmapPlatformDevice* device = Create(width, height, is_opaque);
+  if (!is_opaque)
+    device->accessBitmap(true).eraseARGB(0, 0, 0, 0);
+  return device;
+}
+
 BitmapPlatformDevice* BitmapPlatformDevice::Create(int width, int height,
                                                    bool is_opaque,
                                                    uint8_t* data) {
   SkBitmap bitmap;
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
-  if (data) {
+  if (data)
     bitmap.setPixels(data);
-  } else {
-    if (!bitmap.allocPixels())
-      return NULL;
-    // Follow the logic in SkCanvas::createDevice(), initialize the bitmap if it
-    // is not opaque.
-    if (!is_opaque)
-      bitmap.eraseARGB(0, 0, 0, 0);
-  }
+  else if (!bitmap.allocPixels())
+    return NULL;
+
   bitmap.setIsOpaque(is_opaque);
   return new BitmapPlatformDevice(bitmap);
 }