Enable gpu Debug markers if tracing category skia.gpu is enabled

src/gpu/GrContext.cpp

Index: src/gpu/GrContext.cpp
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 95e0d51cf8979dae8c9a6eaf7cfbd9956d42c540..b701e9e9dc30308a9ad047ebdf52d57ecc67adf1 100755
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -110,7 +110,15 @@ GrContext::GrContext() {
     fOvalRenderer = NULL;
     fViewMatrix.reset();
     fMaxTextureSizeOverride = 1 << 20;
-    fGpuTracingEnabled = false;
+
+    // Check if the gpu.serivce category is set from tracing and enable GpuTracing if it is

[bsalomon, 2014/08/04 15:22:05]

Is it really right to do this only when the GrContext is created? In practice I
think that has usually already occurred before tracing is invoked.

+    const unsigned char *category_enabled = TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(
+        TRACE_DISABLED_BY_DEFAULT("gpu.service"));
+    if (*category_enabled != 0) {
+        fGpuTracingEnabled = true;
+    } else {
+         fGpuTracingEnabled = false;
+    }
 }
 
 bool GrContext::init(GrBackend backend, GrBackendContext backendContext) {