Avoid OOB memcpy in chrome_pdf::CopyImage.

ppapi/cpp/image_data.cc

Index: ppapi/cpp/image_data.cc
diff --git a/ppapi/cpp/image_data.cc b/ppapi/cpp/image_data.cc
index d9738964795eb698d8d612a1b2964f1164594415..90b7c97ab814657da61d28b08ee1d549252c62a0 100644
--- a/ppapi/cpp/image_data.cc
+++ b/ppapi/cpp/image_data.cc
@@ -74,6 +74,11 @@ uint32_t* ImageData::GetAddr32(const Point& coord) {
       &static_cast<char*>(data())[coord.y() * stride() + coord.x() * 4]);
 }
 
+bool ImageData::Contains(const pp::Rect& rect) const {
+  return rect.width() >= 0 && rect.height() >= 0 &&
+      pp::Rect(size()).Contains(rect);
+}
+
 // static
 bool ImageData::IsImageDataFormatSupported(PP_ImageDataFormat format) {
   if (!has_interface<PPB_ImageData_1_0>())