gpu: Workaround Adreno 420 bug with deleting current FBO.

gpu/command_buffer/service/framebuffer_manager.cc

Index: gpu/command_buffer/service/framebuffer_manager.cc
diff --git a/gpu/command_buffer/service/framebuffer_manager.cc b/gpu/command_buffer/service/framebuffer_manager.cc
index d766abb96f04934f5e75464fa58b1d7f85a04aae..905a817eb1e46924cd1c1334b8326c176caf6d8c 100644
--- a/gpu/command_buffer/service/framebuffer_manager.cc
+++ b/gpu/command_buffer/service/framebuffer_manager.cc
@@ -631,6 +631,14 @@ void FramebufferManager::RemoveFramebuffer(GLuint client_id) {
   }
 }
 
+void Framebuffer::UnbindAttachments(GLenum target) {
+  // Replace all attachments with the default Renderbuffer.
+  for (AttachmentMap::const_iterator it = attachments_.begin();
+       it != attachments_.end(); ++it) {
+    glFramebufferRenderbufferEXT(target, it->first, GL_RENDERBUFFER, 0);
+  }
+}
+
 void Framebuffer::AttachRenderbuffer(
     GLenum attachment, Renderbuffer* renderbuffer) {
   const Attachment* a = GetAttachment(attachment);