Restore gl scissor state when switching FBO targets on Qualcomm

This works around flickering on Qualcomm devices when
using virtual contexts. Qualcomm has a bug where switching
to FBO targets of different sizes corrupts the scissor rect.

BUG=165493

Review URL: https://chromiumcodereview.appspot.com/11734037

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175630 0039d316-1c4b-4281-b951-d872f2087c98

gpu/command_buffer/service/feature_info.cc

@@ -91,6 +91,7 @@ FeatureInfo::Workarounds::Workarounds()
       reverse_point_sprite_coord_origin(false),
       set_texture_filter_before_generating_mipmap(false),
       use_current_program_after_successful_link(false),
+      restore_scissor_on_fbo_change(false),
       max_texture_size(0),
       max_cube_map_texture_size(0) {
 }
@@ -598,6 +599,10 @@ void FeatureInfo::AddFeatures() {
       workarounds_.use_current_program_after_successful_link = true;
     }
 
+    if (is_qualcomm) {
+      workarounds_.restore_scissor_on_fbo_change = true;
+    }
+
 #if defined(OS_MACOSX)
     workarounds_.needs_offscreen_buffer_workaround = is_nvidia;
     workarounds_.needs_glsl_built_in_function_emulation = is_amd;

gpu/command_buffer/service/feature_info.h

@@ -53,6 +53,7 @@ class GPU_EXPORT FeatureInfo : public base::RefCounted<FeatureInfo> {
     bool reverse_point_sprite_coord_origin;
     bool set_texture_filter_before_generating_mipmap;
     bool use_current_program_after_successful_link;
+    bool restore_scissor_on_fbo_change;
 
     // Note: 0 here means use driver limit.
     GLint max_texture_size;

gpu/command_buffer/service/gles2_cmd_decoder.cc

@@ -598,6 +598,7 @@ class GLES2DecoderImpl : public GLES2Decoder {
   virtual error::ContextLostReason GetContextLostReason() OVERRIDE;
 
  private:
+  friend class ScopedFrameBufferBinder;
   friend class ScopedGLErrorSuppressor;
   friend class ScopedResolvedFrameBufferBinder;
   friend class ScopedTextureUploadTimer;
@@ -624,6 +625,9 @@ class GLES2DecoderImpl : public GLES2Decoder {
   bool GenVertexArraysOESHelper(GLsizei n, const GLuint* client_ids);
   void DeleteVertexArraysOESHelper(GLsizei n, const GLuint* client_ids);
 
+  // Workarounds
+  void OnFboChanged() const;
+
   // TODO(gman): Cache these pointers?
   BufferManager* buffer_manager() {
     return group_->buffer_manager();
@@ -1743,6 +1747,7 @@ ScopedFrameBufferBinder::ScopedFrameBufferBinder(GLES2DecoderImpl* decoder,
     : decoder_(decoder) {
   ScopedGLErrorSuppressor suppressor(decoder_);
   glBindFramebufferEXT(GL_FRAMEBUFFER, id);
+  decoder->OnFboChanged();
 }
 
 ScopedFrameBufferBinder::~ScopedFrameBufferBinder() {
@@ -2605,6 +2610,7 @@ void GLES2DecoderImpl::DeleteFramebuffersHelper(
             GL_READ_FRAMEBUFFER_EXT : GL_FRAMEBUFFER;
         glBindFramebufferEXT(target, GetBackbufferServiceId());
       }
+      OnFboChanged();
       RemoveFramebufferInfo(client_ids[ii]);
     }
   }
@@ -2761,6 +2767,7 @@ void GLES2DecoderImpl::RestoreCurrentFramebufferBindings() {
         state_.bound_draw_framebuffer.get(),
         GetBackbufferServiceId());
   }
+  OnFboChanged();
 }
 
 void GLES2DecoderImpl::RestoreCurrentTexture2DBindings() {
@@ -3580,6 +3587,13 @@ void GLES2DecoderImpl::RestoreState() const {
       state_.bound_draw_framebuffer->service_id() :
       GetBackbufferServiceId();
   glBindFramebufferEXT(GL_FRAMEBUFFER, service_id);
+  OnFboChanged();
+}
+
+void GLES2DecoderImpl::OnFboChanged() const {
+  if (workarounds().restore_scissor_on_fbo_change)
+    glScissor(state_.scissor_x, state_.scissor_y,
+              state_.scissor_width, state_.scissor_height);
 }
 
 void GLES2DecoderImpl::DoBindFramebuffer(GLenum target, GLuint client_id) {
@@ -3625,6 +3639,7 @@ void GLES2DecoderImpl::DoBindFramebuffer(GLenum target, GLuint client_id) {
   }
 
   glBindFramebufferEXT(target, service_id);
+  OnFboChanged();
 }
 
 void GLES2DecoderImpl::DoBindRenderbuffer(GLenum target, GLuint client_id) {