Tag TransportDIBs with the device scale factor they expect.

content/browser/renderer_host/backing_store_manager.cc

Index: content/browser/renderer_host/backing_store_manager.cc
diff --git a/content/browser/renderer_host/backing_store_manager.cc b/content/browser/renderer_host/backing_store_manager.cc
index e3b4a03a46dcb65ce0e5618bfe35deb47673d95d..80d6393744380f8164c7d64ba1f47e0180bde9cc 100644
--- a/content/browser/renderer_host/backing_store_manager.cc
+++ b/content/browser/renderer_host/backing_store_manager.cc
@@ -198,6 +198,7 @@ void BackingStoreManager::PrepareBackingStore(
     TransportDIB::Id bitmap,
     const gfx::Rect& bitmap_rect,
     const std::vector<gfx::Rect>& copy_rects,
+    float scale_factor,
     const base::Closure& completion_callback,
     bool* needs_full_paint,
     bool* scheduled_completion_callback) {
@@ -219,7 +220,7 @@ void BackingStoreManager::PrepareBackingStore(
   }
 
   backing_store->PaintToBackingStore(host->GetProcess(), bitmap,
-                                     bitmap_rect, copy_rects,
+                                     bitmap_rect, copy_rects, scale_factor,
                                      completion_callback,
                                      scheduled_completion_callback);
 }