Enable deferred free for syzyasan builds behind a feature.

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index 0f156e6f0b470b1b38ec234a100ea8323139c2ff..ee481a14a7970c3165036e99f9cf40d37edaf2b4 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -90,6 +90,7 @@
 #include "chrome/browser/ui/webui/chrome_web_ui_controller_factory.h"
 #include "chrome/common/channel_info.h"
 #include "chrome/common/chrome_constants.h"
+#include "chrome/common/chrome_features.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_result_codes.h"
 #include "chrome/common/chrome_switches.h"
@@ -1182,6 +1183,28 @@ void ChromeBrowserMainParts::PreBrowserStart() {
 
   three_d_observer_.reset(new ThreeDAPIObserver());
 
+#if defined(SYZYASAN)
+  // Enable the deferred free mechanism in the syzyasan module, which helps the
+  // performance by deferring some work on the critical path to a background
+  // thread.
+  if (base::FeatureList::IsEnabled(features::kSyzyasanDeferredFree)) {
+    typedef VOID(WINAPI * SyzyasanEnableDeferredFreeThreadFunc)(VOID);
+    HMODULE SyzyasanModuleHandle = ::GetModuleHandle(L"syzyasan_rtl.dll");

[chrisha, 2016/03/17 18:35:28]

euhh... snake_style variable names instead of CamelCase?

[Georges Khalil, 2016/03/17 19:34:39]

Oops, I was looking at Windows code for too long :S

Done.

+    bool success = false;
+    if (SyzyasanModuleHandle) {
+      SyzyasanEnableDeferredFreeThreadFunc EnableDeferredFreeThread =

[chrisha, 2016/03/17 18:35:28]

ditto

[Georges Khalil, 2016/03/17 19:34:39]

Done.

+          reinterpret_cast<SyzyasanEnableDeferredFreeThreadFunc>(
+              ::GetProcAddress(SyzyasanModuleHandle,
+                               "asan_EnableDeferredFreeThread"));
+      if (EnableDeferredFreeThread) {
+        EnableDeferredFreeThread();
+        success = true;
+      }
+    }
+    UMA_HISTOGRAM_BOOLEAN("Syzyasan.DeferredFreeWasEnabled", success);
+  }
+#endif
+
 // Start the tab manager here so that we give the most amount of time for the
 // other services to start up before we start adjusting the oom priority.
 #if defined(OS_WIN) || defined(OS_MACOSX) || defined(OS_CHROMEOS)