Fix partial updates of transparent plugin backgrounds on Mac

chrome/plugin/webplugin_proxy.cc

Index: chrome/plugin/webplugin_proxy.cc
diff --git a/chrome/plugin/webplugin_proxy.cc b/chrome/plugin/webplugin_proxy.cc
index ab5326fd1977c2151055d8fd3d2c608098905bd6..9983315e8c39f16e7c938358bbf4012b2393e92c 100644
--- a/chrome/plugin/webplugin_proxy.cc
+++ b/chrome/plugin/webplugin_proxy.cc
@@ -422,8 +422,11 @@ void WebPluginProxy::Paint(const gfx::Rect& rect) {
   } else {
     scoped_cftyperef<CGImageRef> image(
         CGBitmapContextCreateImage(background_context_));
+    CGRect source_rect = rect.ToCGRect();
+    // Flip the rect we use to pull from the canvas, since it's upside-down.
+    source_rect.origin.y = CGImageGetHeight(image) - rect.y() - rect.height();
     scoped_cftyperef<CGImageRef> sub_image(
-        CGImageCreateWithImageInRect(image, rect.ToCGRect()));
+        CGImageCreateWithImageInRect(image, source_rect));
     CGContextDrawImage(windowless_context_, rect.ToCGRect(), sub_image);
   }
   CGContextClipToRect(windowless_context_, rect.ToCGRect());