Report user actions when gesture starts and stops in user_model.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index a62dd41541c5343e403e75a244ebf5bf2d22212d..7a0a4dadd38201004914b396a76a54ca007b0ad3 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -635,6 +635,11 @@ RenderThreadImpl::RenderThreadImpl(
 void RenderThreadImpl::Init() {
   TRACE_EVENT0("startup", "RenderThreadImpl::Init");
 
+  base::RemoveActionCallback(action_callback_);
+  action_callback_ = base::Bind(&RenderThreadImpl::RecordComputedAction,
+                                base::Unretained(this));
+  base::AddActionCallback(action_callback_);
+
   base::trace_event::TraceLog::GetInstance()->SetThreadSortIndex(
       base::PlatformThread::CurrentId(),
       kTraceEventRendererMainThreadSortIndex);
@@ -858,6 +863,7 @@ void RenderThreadImpl::Init() {
 }
 
 RenderThreadImpl::~RenderThreadImpl() {
+  base::RemoveActionCallback(action_callback_);
 }
 
 void RenderThreadImpl::Shutdown() {