Added a simple smoke test for Graphics3D. It attempts to exercise the entire graphics-3d pipeline...

ppapi/tests/test_graphics_3d.h

Index: ppapi/tests/test_graphics_3d.h
===================================================================
--- ppapi/tests/test_graphics_3d.h	(revision 99012)
+++ ppapi/tests/test_graphics_3d.h	(working copy)
@@ -19,6 +19,14 @@
   virtual void RunTest();
 
  private:
+  // Various tests.
+  std::string TestFrame();
+
+  // Utils used by various tests.
+  int32_t SwapBuffersSync(PP_Resource context);
+  std::string TestPixel(PP_Resource context,
+                        int x, int y, const uint8_t expected_color[4]);
+
   // Used by the tests that access the C API directly.
   const PPB_Graphics3D_Dev* graphics_3d_;
   const PPB_OpenGLES2_Dev* opengl_es2_;