Implement EXT_draw_buffers WebGL extention support in command buffer.

gpu/command_buffer/service/framebuffer_manager.cc

Index: gpu/command_buffer/service/framebuffer_manager.cc
===================================================================
--- gpu/command_buffer/service/framebuffer_manager.cc	(revision 187725)
+++ gpu/command_buffer/service/framebuffer_manager.cc	(working copy)
@@ -198,10 +198,13 @@
   DISALLOW_COPY_AND_ASSIGN(TextureAttachment);
 };
 
-FramebufferManager::FramebufferManager()
+FramebufferManager::FramebufferManager(uint32 max_draw_buffers)
     : framebuffer_state_change_count_(1),
       framebuffer_count_(0),
-      have_context_(true) {
+      have_context_(true),
+      max_draw_buffers_(max_draw_buffers) {
+  if (max_draw_buffers_ < 1)
+    max_draw_buffers_ = 1;
 }
 
 FramebufferManager::~FramebufferManager() {
@@ -254,6 +257,11 @@
       has_been_bound_(false),
       framebuffer_complete_state_count_id_(0) {
   manager->StartTracking(this);
+  DCHECK_GT(manager->max_draw_buffers_, 0u);
+  draw_buffers_.reset(new GLenum[manager->max_draw_buffers_]);
+  draw_buffers_[0] = GL_COLOR_ATTACHMENT0;
+  for (uint32 i = 1; i < manager->max_draw_buffers_; ++i)
+    draw_buffers_[i] = GL_NONE;
 }
 
 Framebuffer::~Framebuffer() {
@@ -402,6 +410,20 @@
   return true;
 }
 
+GLenum Framebuffer::GetDrawBuffer(GLenum draw_buffer) const {
+  GLsizei index = static_cast<GLsizei>(
+      draw_buffer - GL_DRAW_BUFFER0_ARB);
+  CHECK(index >= 0 &&
+        index < static_cast<GLsizei>(manager_->max_draw_buffers_));
+  return draw_buffers_[index];
+}
+
+void Framebuffer::SetDrawBuffers(GLsizei n, const GLenum* bufs) {
+  DCHECK(n <= static_cast<GLsizei>(manager_->max_draw_buffers_));
+  for (GLsizei i = 0; i < n; ++i)
+    draw_buffers_[i] = bufs[i];
+}
+
 void Framebuffer::UnbindRenderbuffer(
     GLenum target, Renderbuffer* renderbuffer) {
   bool done;
@@ -456,10 +478,6 @@
 
 void Framebuffer::AttachRenderbuffer(
     GLenum attachment, Renderbuffer* renderbuffer) {
-  DCHECK(attachment == GL_COLOR_ATTACHMENT0 ||
-         attachment == GL_DEPTH_ATTACHMENT ||
-         attachment == GL_STENCIL_ATTACHMENT ||
-         attachment == GL_DEPTH_STENCIL_ATTACHMENT);
   const Attachment* a = GetAttachment(attachment);
   if (a)
     a->DetachFromFramebuffer();
@@ -475,10 +493,6 @@
 void Framebuffer::AttachTexture(
     GLenum attachment, Texture* texture, GLenum target,
     GLint level) {
-  DCHECK(attachment == GL_COLOR_ATTACHMENT0 ||
-         attachment == GL_DEPTH_ATTACHMENT ||
-         attachment == GL_STENCIL_ATTACHMENT ||
-         attachment == GL_DEPTH_STENCIL_ATTACHMENT);
   const Attachment* a = GetAttachment(attachment);
   if (a)
     a->DetachFromFramebuffer();