content: Add command line flag for native GPU memory buffers.

cc/test/test_web_graphics_context_3d.h

Index: cc/test/test_web_graphics_context_3d.h
diff --git a/cc/test/test_web_graphics_context_3d.h b/cc/test/test_web_graphics_context_3d.h
index ff2c7049eaa263fb7ec958315b4b113178f96275..56c17c097a2c1111bd4876fdcbed5ce81684c84b 100644
--- a/cc/test/test_web_graphics_context_3d.h
+++ b/cc/test/test_web_graphics_context_3d.h
@@ -330,6 +330,9 @@ class TestWebGraphicsContext3D {
   void set_support_image(bool support) {
     test_capabilities_.gpu.image = support;
   }
+  void set_support_texture_rectangle(bool support) {
+    test_capabilities_.gpu.texture_rectangle = support;
+  }
 
   // When this context is lost, all contexts in its share group are also lost.
   void add_share_group_context(TestWebGraphicsContext3D* context3d) {