Force time elapsed queries on certain drivers.

ui/gl/gpu_timing.cc

Index: ui/gl/gpu_timing.cc
diff --git a/ui/gl/gpu_timing.cc b/ui/gl/gpu_timing.cc
index 45908c985188f56baaac43086cc62e9c01929248..8ef6abd569b7a40780776ef9527b7cdf1cb1a9c4 100644
--- a/ui/gl/gpu_timing.cc
+++ b/ui/gl/gpu_timing.cc
@@ -27,6 +27,7 @@ class GPUTimingImpl : public GPUTiming {
 
   void ForceTimeElapsedQuery() { force_time_elapsed_query_ = true; }
   bool IsForceTimeElapsedQuery() { return force_time_elapsed_query_; }
+  bool ShouldForceTimeElapsedQuery();
 
   GPUTiming::TimerType GetTimerType() const { return timer_type_; }
 
@@ -317,13 +318,31 @@ GPUTimingImpl::GPUTimingImpl(GLContextReal* context) {
     timer_type_ = GPUTiming::kTimerTypeARB;
   } else if (context->HasExtension("GL_EXT_timer_query")) {
     timer_type_ = GPUTiming::kTimerTypeEXT;
-    force_time_elapsed_query_ = true;
   }
+  force_time_elapsed_query_ = ShouldForceTimeElapsedQuery();
 }
 
 GPUTimingImpl::~GPUTimingImpl() {
 }
 
+bool GPUTimingImpl::ShouldForceTimeElapsedQuery() {
+  if (timer_type_ == GPUTiming::kTimerTypeInvalid) {
+    return false;
+  } else if (timer_type_ == GPUTiming::kTimerTypeEXT) {
+    // GL_EXT_timer_query does not support timestamps
+    return true;
+  } else {
+    // Certain drivers such as Mac drivers and ANGLE's D3D11 backend do not
+    // support timestamps even though queries for them are valid. This is
+    // indicated by returning 0 when for GL_TIMESTAMP in GL_QUERY_COUNTER_BITS
+    DCHECK(timer_type_ == GPUTiming::kTimerTypeARB ||
+           timer_type_ == GPUTiming::kTimerTypeDisjoint);
+    GLint timestamp_bits;

[David Yen, 2016/02/11 17:53:20]

Could we just make these 3 lines a static function outside of the class? Then
just call that function in after lines 316 and 318?

+    glGetQueryiv(GL_TIMESTAMP, GL_QUERY_COUNTER_BITS, &timestamp_bits);
+    return (timestamp_bits == 0);
+  }
+}
+
 uint32_t GPUTimingImpl::GetDisjointCount() {
   if (timer_type_ == GPUTiming::kTimerTypeDisjoint) {
     GLint disjoint_value = 0;