Optionally clear PlatformCanvas instances.

skia/ext/bitmap_platform_device_win.cc

Index: skia/ext/bitmap_platform_device_win.cc
===================================================================
--- skia/ext/bitmap_platform_device_win.cc	(revision 123041)
+++ skia/ext/bitmap_platform_device_win.cc	(working copy)
@@ -91,8 +91,9 @@
     HDC screen_dc,
     int width,
     int height,
-    bool is_opaque,
+    int flags,
     HANDLE shared_section) {
+
   SkBitmap bitmap;
 
   // CreateDIBSection appears to get unhappy if we create an empty bitmap, so
@@ -126,18 +127,19 @@
 
   bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
   bitmap.setPixels(data);
-  bitmap.setIsOpaque(is_opaque);
+  bitmap.setIsOpaque(flags & FLAGS_OPAQUE);
 
   // If we were given data, then don't clobber it!
   if (!shared_section) {
-    if (is_opaque) {
+    if (flags & FLAGS_OPAQUE) {
 #ifndef NDEBUG
       // To aid in finding bugs, we set the background color to something
       // obviously wrong so it will be noticable when it is not cleared
       bitmap.eraseARGB(255, 0, 255, 128);  // bright bluish green
 #endif
     } else {
-      bitmap.eraseARGB(0, 0, 0, 0);
+      if (flags & FLAGS_INITIALIZED)
+        bitmap.eraseARGB(0, 0, 0, 0);
     }
   }
 
@@ -150,11 +152,11 @@
 // static
 BitmapPlatformDevice* BitmapPlatformDevice::create(int width,
                                                    int height,
-                                                   bool is_opaque,
+                                                   int flags,
                                                    HANDLE shared_section) {
   HDC screen_dc = GetDC(NULL);
   BitmapPlatformDevice* device = BitmapPlatformDevice::create(
-      screen_dc, width, height, is_opaque, shared_section);
+      screen_dc, width, height, flags, shared_section);
   ReleaseDC(NULL, screen_dc);
   return device;
 }
@@ -259,7 +261,9 @@
     SkBitmap::Config config, int width, int height, bool isOpaque,
     Usage /*usage*/) {
   SkASSERT(config == SkBitmap::kARGB_8888_Config);
-  return BitmapPlatformDevice::create(width, height, isOpaque, NULL);
+  return BitmapPlatformDevice::create(width, height,
+                                      GetDefaultFlags(isOpaque),
+                                      NULL);
 }
 
 }  // namespace skia