Draw WebVR security overlay with a non-reprojected viewport

chrome/browser/android/vr_shell/vr_shell.cc

Index: chrome/browser/android/vr_shell/vr_shell.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell.cc b/chrome/browser/android/vr_shell/vr_shell.cc
index 9f1bb69260ffe0abdcdd3bbe6189d19fcd743a16..89e6a0082881c75849c1acc03141ea0491e63546 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -245,13 +245,33 @@ void VrShell::InitializeGl(JNIEnv* env,
   std::vector<gvr::BufferSpec> specs;
   specs.push_back(gvr_api_->CreateBufferSpec());
   render_size_ = specs[0].GetSize();
+
+  // For WebVR content
+  specs.push_back(gvr_api_->CreateBufferSpec());
+
   swap_chain_.reset(new gvr::SwapChain(gvr_api_->CreateSwapChain(specs)));
 
   vr_shell_renderer_.reset(new VrShellRenderer());
   buffer_viewport_list_.reset(
       new gvr::BufferViewportList(gvr_api_->CreateEmptyBufferViewportList()));
+  buffer_viewport_list_->SetToRecommendedBufferViewports();
+
   buffer_viewport_.reset(
       new gvr::BufferViewport(gvr_api_->CreateBufferViewport()));
+
+  overlay_left_viewport_.reset(
+      new gvr::BufferViewport(gvr_api_->CreateBufferViewport()));
+  buffer_viewport_list_->GetBufferViewport(GVR_LEFT_EYE,
+                                           overlay_left_viewport_.get());
+  overlay_left_viewport_->SetSourceBufferIndex(1);
+  overlay_left_viewport_->SetReprojection(GVR_REPROJECTION_NONE);
+
+  overlay_right_viewport_.reset(
+      new gvr::BufferViewport(gvr_api_->CreateBufferViewport()));
+  buffer_viewport_list_->GetBufferViewport(GVR_RIGHT_EYE,
+                                           overlay_right_viewport_.get());
+  overlay_right_viewport_->SetSourceBufferIndex(1);
+  overlay_right_viewport_->SetReprojection(GVR_REPROJECTION_NONE);
 }
 
 void VrShell::UpdateController(const gvr::Vec3f& forward_vector) {
@@ -422,6 +442,13 @@ void VrShell::DrawFrame(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   if (webvr_mode_) {
     DrawWebVr();
     if (!webvr_secure_origin_) {
+      buffer_viewport_list_->SetBufferViewport(buffer_viewport_list_->GetSize(),
+          *overlay_left_viewport_);
+      buffer_viewport_list_->SetBufferViewport(buffer_viewport_list_->GetSize(),

[klausw (use chromium instead), 2016/10/17 23:03:18]

Using GetSize() twice seems weird. Does the SetToRecommendedBufferViewports()
above create a two-element list (0=left eye, 1=right eye), and this appends
items 2=overlay left, 3=overlay right?

+          *overlay_right_viewport_);
+
+      // Bind back to the second default framebuffer.

[klausw (use chromium instead), 2016/10/17 23:03:18]

These comments are confusing. Can you rephrase this one and the one above to
something like this?

// Render to the main viewport set.
frame.BindBuffer(0);
...
// Render to the overlay viewport set.
frame.BindBuffer(1);

For bonus points, use a constant instead of a hardcoded "1" here and in
SetSourceBufferIndex above?

+      frame.BindBuffer(1);
       DrawWebVrOverlay(target_time.monotonic_system_time_nanos);
     }
 
@@ -639,6 +666,9 @@ void VrShell::DrawWebVrOverlay(int64_t present_time_nanos) {
   gvr::Mat4f right_eye_view_matrix =
       gvr_api_->GetEyeFromHeadMatrix(GVR_RIGHT_EYE);
 
+  // Don't need to clear, since we're drawing over the entire render target.

[klausw (use chromium instead), 2016/10/17 23:03:18]

Please delete this comment, it conflicts with the glClear immediately below.

+  glClear(GL_COLOR_BUFFER_BIT);
+
   buffer_viewport_list_->GetBufferViewport(GVR_LEFT_EYE,
                                            buffer_viewport_.get());
   DrawWebVrEye(left_eye_view_matrix, *buffer_viewport_, present_time_nanos);