Send array of paint rects and bitmaps as opposed to a Union

chrome/browser/renderer_host/backing_store_mac.cc

Index: chrome/browser/renderer_host/backing_store_mac.cc
===================================================================
--- chrome/browser/renderer_host/backing_store_mac.cc	(revision 17347)
+++ chrome/browser/renderer_host/backing_store_mac.cc	(working copy)
@@ -21,14 +21,24 @@
 
 void BackingStore::PaintRect(base::ProcessHandle process,
                              TransportDIB* bitmap,
-                             const gfx::Rect& bitmap_rect) {
+                             const gfx::Rect& bitmap_rect,
+                             const gfx::Rect& paint_rect) {
+  DCHECK(bitmap_rect.Contains(paint_rect) &&
+         paint_rect.x() < kMaxBitmapLengthAllowed &&
+         paint_rect.y() < kMaxBitmapLengthAllowed);
   SkBitmap skbitmap;
   skbitmap.setConfig(SkBitmap::kARGB_8888_Config, bitmap_rect.width(),
                      bitmap_rect.height(), 4 * bitmap_rect.width());
 
   skbitmap.setPixels(bitmap->memory());
-
-  canvas_.drawBitmap(skbitmap, bitmap_rect.x(), bitmap_rect.y());
+  SkIRect src_rect;
+  src_rect.set(paint_rect.x(), paint_rect.y(),
+               paint_rect.right(), paint_rect.bottom());
+  src_rect.offset(-bitmap_rect.x(), -bitmap_rect.y());
+  SkRect dst_rect;
+  dst_rect.iset(paint_rect.x(), paint_rect.y(),
+                paint_rect.right(), paint_rect.bottom());
+  canvas_.drawBitmapRect(skbitmap, &src_rect, dst_rect);
 }
 
 void BackingStore::ScrollRect(base::ProcessHandle process,
@@ -117,6 +127,6 @@
   }
 
   // Now paint the new bitmap data.
-  PaintRect(process, bitmap, bitmap_rect);
+  PaintRect(process, bitmap, bitmap_rect, bitmap_rect);
   return;
 }