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

chrome/browser/renderer_host/backing_store.h

Index: chrome/browser/renderer_host/backing_store.h
===================================================================
--- chrome/browser/renderer_host/backing_store.h	(revision 17347)
+++ chrome/browser/renderer_host/backing_store.h	(working copy)
@@ -63,9 +63,12 @@
 #endif
 
   // Paints the bitmap from the renderer onto the backing store.
+  // bitmap_rect is the rect of the whole bitmap, and paint_rect
+  // is a sub-rect of bitmap that we want to draw.
   void PaintRect(base::ProcessHandle process,
                  TransportDIB* bitmap,
-                 const gfx::Rect& bitmap_rect);
+                 const gfx::Rect& bitmap_rect,
+                 const gfx::Rect& paint_rect);
 
   // Scrolls the given rect in the backing store, replacing the given region
   // identified by |bitmap_rect| by the bitmap in the file identified by the
@@ -95,8 +98,11 @@
 #elif defined(OS_LINUX)
   // Paints the bitmap from the renderer onto the backing store without
   // using Xrender to composite the pixmaps.
+  // bitmap_rect is the rect of the whole bitmap, and paint_rect
+  // is a sub-rect of bitmap that we want to draw.
   void PaintRectWithoutXrender(TransportDIB* bitmap,
-                               const gfx::Rect& bitmap_rect);
+                               const gfx::Rect& bitmap_rect,
+                               const gfx::Rect& paint_rect);
 
   // This is the connection to the X server where this backing store will be
   // displayed.
@@ -119,6 +125,10 @@
   void* pixmap_gc_;
 #endif
 
+  // Sanity checks on the size of the rects to draw so that we don't allocate
+  // enourmous pixmaps.
+  static int kMaxBitmapLengthAllowed;
+
   DISALLOW_COPY_AND_ASSIGN(BackingStore);
 };
 
@@ -158,6 +168,7 @@
                                            base::ProcessHandle process_handle,
                                            TransportDIB* bitmap,
                                            const gfx::Rect& bitmap_rect,
+                                           const gfx::Rect& paint_rect,
                                            bool* needs_full_paint);
 
   // Returns a matching backing store for the host.