Avoid null-pointer dereference for PPAPI Instance BindGraphics....

webkit/plugins/ppapi/ppapi_plugin_instance.cc

Index: webkit/plugins/ppapi/ppapi_plugin_instance.cc
===================================================================
--- webkit/plugins/ppapi/ppapi_plugin_instance.cc	(revision 72376)
+++ webkit/plugins/ppapi/ppapi_plugin_instance.cc	(working copy)
@@ -460,16 +460,18 @@
       // repaints.
       const SkBitmap* old_backing_bitmap =
           bound_graphics_2d()->image_data()->GetMappedBitmap();
-      SkRect old_size = SkRect::MakeWH(
-          SkScalar(static_cast<float>(old_backing_bitmap->width())),
-          SkScalar(static_cast<float>(old_backing_bitmap->height())));
+      if (old_backing_bitmap != NULL) {

[neb, 2011/01/24 21:32:21]

Shouldn't it fail if NULL? That should not be possible short of internal error
or malicious code.

+        SkRect old_size = SkRect::MakeWH(
+            SkScalar(static_cast<float>(old_backing_bitmap->width())),
+            SkScalar(static_cast<float>(old_backing_bitmap->height())));
 
-      SkCanvas canvas(*graphics_2d->image_data()->GetMappedBitmap());
-      canvas.drawBitmap(*old_backing_bitmap, 0, 0);
+        SkCanvas canvas(*graphics_2d->image_data()->GetMappedBitmap());
+        canvas.drawBitmap(*old_backing_bitmap, 0, 0);
 
-      // Fill in any extra space with white.
-      canvas.clipRect(old_size, SkRegion::kDifference_Op);
-      canvas.drawARGB(255, 255, 255, 255);
+        // Fill in any extra space with white.
+        canvas.clipRect(old_size, SkRegion::kDifference_Op);
+        canvas.drawARGB(255, 255, 255, 255);
+      }
     }
 
     bound_graphics_ = graphics_2d;