gpu, cmaa: add glApplyScreenSpaceAntialiasingCHROMIUM unittests

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index f6c5916e198bec66ef77b65ba17b3988f8d5858c..f905150914dc9b513738a3901fcc9cca35ecff90 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -16776,6 +16776,17 @@ void GLES2DecoderImpl::DoCreateAndConsumeTextureINTERNAL(
 }
 
 void GLES2DecoderImpl::DoApplyScreenSpaceAntialiasingCHROMIUM() {
+  Framebuffer* bound_framebuffer =
+      GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER);
+  // TODO(dshwang): support it even after glBindFrameBuffer(GL_FRAMEBUFFER, 0).
+  // skia will need to render to the window. crbug.com/656618
+  if (!bound_framebuffer) {
+    LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION,
+                       "glApplyScreenSpaceAntialiasingCHROMIUM",
+                       "no bound framebuffer object");
+    return;
+  }
+
   // Apply CMAA(Conservative Morphological Anti-Aliasing) algorithm to the
   // color attachments of currently bound draw framebuffer.
   // Reference GL_INTEL_framebuffer_CMAA for details.
@@ -16798,8 +16809,7 @@ void GLES2DecoderImpl::DoApplyScreenSpaceAntialiasingCHROMIUM() {
         return;
     }
     apply_framebuffer_attachment_cmaa_intel_
-        ->ApplyFramebufferAttachmentCMAAINTEL(
-            this, GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER));
+        ->ApplyFramebufferAttachmentCMAAINTEL(this, bound_framebuffer);
   }
 }