WebVR: Add sanity checks for decoded pose index values

third_party/WebKit/Source/modules/vr/VRDisplay.cpp

Index: third_party/WebKit/Source/modules/vr/VRDisplay.cpp
diff --git a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
index c286f069f65efba7d5c194963e6b69a5bd3a168b..3250eb45808d45f826d885811fb4ce388004f173 100644
--- a/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
+++ b/third_party/WebKit/Source/modules/vr/VRDisplay.cpp
@@ -612,8 +612,10 @@ void VRDisplay::submitFrame() {
   gl->ColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
   int idx = m_framePose->poseIndex;
   // Careful with the arithmetic here. Float color 1.f is equivalent to int 255.
-  gl->ClearColor((idx & 255) / 255.0f, ((idx >> 8) & 255) / 255.0f,
-                 ((idx >> 16) & 255) / 255.0f, 1.0f);
+  // Use the low byte of the index as the red component, and store an arbitrary
+  // magic number in green/blue. This number must match the reading code in
+  // vr_shell.cc. Avoid all-black/all-white.
+  gl->ClearColor((idx & 255) / 255.0f, 42 / 255.0f, 142 / 255.0f, 1.0f);

[mthiesse, 2016/12/01 21:53:15]

Make constants for the magic numbers, here and in vr_shell

[klausw, 2016/12/01 22:36:04]

Done.

   gl->Clear(GL_COLOR_BUFFER_BIT);
 
   // Set the GL state back to what was set by the WebVR application.