Remove constructors of TraceEventHandle

The constructors of TraceEventHandle makes the constructor of
ScopedTracer (which is called even when tracing is not enabled)
initialize the Data structure which we wanted to avoid.

BUG=trace-viewer:489
R=dsinclair@chromium.org

Review URL: https://codereview.chromium.org/33423006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230224 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 20 insertions, 23 deletions

diff --git a/base/debug/trace_event_impl.cc b/base/debug/trace_event_impl.cc
index 651ee56..69dcfdca 100644
--- a/base/debug/trace_event_impl.cc
+++ b/base/debug/trace_event_impl.cc
@@ -438,6 +438,18 @@ class TraceLog::OptionalAutoLock {
   DISALLOW_COPY_AND_ASSIGN(OptionalAutoLock);
 };
 
+// Use this function instead of TraceEventHandle constructor to keep the
+// overhead of ScopedTracer (trace_event.h) constructor minimum.
+void MakeHandle(uint32 chunk_seq, size_t chunk_index, size_t event_index,
+                TraceEventHandle* handle) {
+  DCHECK(chunk_seq);
+  DCHECK(chunk_index < (1u << 16));
+  DCHECK(event_index < (1u << 16));
+  handle->chunk_seq = chunk_seq;
+  handle->chunk_index = chunk_index;
+  handle->event_index = event_index;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 //
 // TraceEvent
@@ -1049,7 +1061,8 @@ TraceEvent* TraceLog::ThreadLocalEventBuffer::AddTraceEvent(
   size_t event_index;
   TraceEvent* trace_event = chunk_->AddTraceEvent(&event_index);
   if (trace_event && handle)
-    *handle = TraceEventHandle(chunk_->seq(), chunk_index_, event_index);
+    MakeHandle(chunk_->seq(), chunk_index_, event_index, handle);
+
   return trace_event;
 }
 
@@ -1484,8 +1497,8 @@ TraceEvent* TraceLog::AddEventToThreadSharedChunkWhileLocked(
   size_t event_index;
   TraceEvent* trace_event = thread_shared_chunk_->AddTraceEvent(&event_index);
   if (trace_event && handle) {
-    *handle = TraceEventHandle(thread_shared_chunk_->seq(),
-                               thread_shared_chunk_index_, event_index);
+    MakeHandle(thread_shared_chunk_->seq(), thread_shared_chunk_index_,
+               event_index, handle);
   }
   return trace_event;
 }
@@ -1716,7 +1729,7 @@ TraceEventHandle TraceLog::AddTraceEventWithThreadIdAndTimestamp(
     const unsigned long long* arg_values,
     const scoped_refptr<ConvertableToTraceFormat>* convertable_values,
     unsigned char flags) {
-  TraceEventHandle handle;
+  TraceEventHandle handle = { 0, 0, 0 };
   if (!*category_group_enabled)
     return handle;
 
@@ -2011,6 +2024,9 @@ TraceEvent* TraceLog::GetEventByHandle(TraceEventHandle handle) {
 
 TraceEvent* TraceLog::GetEventByHandleInternal(TraceEventHandle handle,
                                                OptionalAutoLock* lock) {
+  if (!handle.chunk_seq)
+    return NULL;
+
   if (thread_local_event_buffer_.Get()) {
     TraceEvent* trace_event =
         thread_local_event_buffer_.Get()->GetEventByHandle(handle);
diff --git a/base/debug/trace_event_impl.h b/base/debug/trace_event_impl.h
index 1d30153..a593f642 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -80,25 +80,6 @@ class ConvertableToTraceFormat : public RefCounted<ConvertableToTraceFormat> {
 };
 
 struct TraceEventHandle {
-  TraceEventHandle()
-      : chunk_seq(0),
-        chunk_index(0),
-        event_index(0) {
-  }
-
-  TraceEventHandle(uint32 a_chunk_seq,
-                   size_t a_chunk_index,
-                   size_t a_event_index)
-      : chunk_seq(a_chunk_seq),
-        chunk_index(static_cast<uint16>(a_chunk_index)),
-        event_index(static_cast<uint16>(a_event_index)) {
-    DCHECK(chunk_seq);
-    DCHECK(a_chunk_index < (1u << 16));
-    DCHECK(a_event_index < (1u << 16));
-  }
-
-  bool IsNull() const { return chunk_seq == 0; }
-
   uint32 chunk_seq;
   uint16 chunk_index;
   uint16 event_index;