Fix gcc 4.6 warnings in gpu.

gpu/command_buffer/client/gles2_implementation_unittest.cc

Index: gpu/command_buffer/client/gles2_implementation_unittest.cc
diff --git a/gpu/command_buffer/client/gles2_implementation_unittest.cc b/gpu/command_buffer/client/gles2_implementation_unittest.cc
index b018a502751b68330a823b6a8eb41dc1859adc52..9bfc9ce51d6304fe76f0bfa68ff9aed62a0db257 100644
--- a/gpu/command_buffer/client/gles2_implementation_unittest.cc
+++ b/gpu/command_buffer/client/gles2_implementation_unittest.cc
@@ -2038,7 +2038,7 @@ TEST_F(GLES2ImplementationTest, TexSubImage2DFlipY) {
   expected.pixel_store_i1.Init(GL_UNPACK_ALIGNMENT, kPixelStoreUnpackAlignment);
   expected.tex_image_2d.Init(
       kTarget, kLevel, kFormat, kTextureWidth, kTextureHeight, kBorder, kFormat,
-      kType, 0, NULL);
+      kType, 0, 0);
   expected.tex_sub_image_2d1.Init(kTarget, kLevel, kSubImageXOffset,
       kSubImageYOffset + 2, kSubImageWidth, 2, kFormat, kType,
       mem1.id, mem1.offset, false);