Implement EXT_draw_buffers WebGL extention support in command buffer.

gpu/command_buffer/service/gles2_cmd_decoder_autogen.h

Index: gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
===================================================================
--- gpu/command_buffer/service/gles2_cmd_decoder_autogen.h	(revision 186778)
+++ gpu/command_buffer/service/gles2_cmd_decoder_autogen.h	(working copy)
@@ -3181,7 +3181,51 @@
   return error::kNoError;
 }
 
+error::Error GLES2DecoderImpl::HandleDrawBuffersEXT(
+    uint32 immediate_data_size, const gles2::cmds::DrawBuffersEXT& c) {
+  GLsizei count = static_cast<GLsizei>(c.count);
+  uint32 data_size;
+  if (!ComputeDataSize(count, sizeof(GLenum), 1, &data_size)) {
+    return error::kOutOfBounds;
+  }
+  const GLenum* bufs = GetSharedMemoryAs<const GLenum*>(
+      c.bufs_shm_id, c.bufs_shm_offset, data_size);
+  if (count < 0) {
+    SetGLError(GL_INVALID_VALUE, "glDrawBuffersEXT", "count < 0");
+    return error::kNoError;
+  }
+  if (bufs == NULL) {
+    return error::kOutOfBounds;
+  }
+  DoDrawBuffersEXT(count, bufs);
+  return error::kNoError;
+}
 
+error::Error GLES2DecoderImpl::HandleDrawBuffersEXTImmediate(
+    uint32 immediate_data_size,
+    const gles2::cmds::DrawBuffersEXTImmediate& c) {
+  GLsizei count = static_cast<GLsizei>(c.count);
+  uint32 data_size;
+  if (!ComputeDataSize(count, sizeof(GLenum), 1, &data_size)) {
+    return error::kOutOfBounds;
+  }
+  if (data_size > immediate_data_size) {
+    return error::kOutOfBounds;
+  }
+  const GLenum* bufs = GetImmediateDataAs<const GLenum*>(
+      c, data_size, immediate_data_size);
+  if (count < 0) {
+    SetGLError(GL_INVALID_VALUE, "glDrawBuffersEXT", "count < 0");
+    return error::kNoError;
+  }
+  if (bufs == NULL) {
+    return error::kOutOfBounds;
+  }
+  DoDrawBuffersEXT(count, bufs);
+  return error::kNoError;
+}
+
+
 bool GLES2DecoderImpl::SetCapabilityState(GLenum cap, bool enabled) {
   switch (cap) {
     case GL_BLEND: