Add stats collection for telemetry startup.warm.blank_page test.

mandoline/ui/browser/browser_manager.cc

Index: mandoline/ui/browser/browser_manager.cc
diff --git a/mandoline/ui/browser/browser_manager.cc b/mandoline/ui/browser/browser_manager.cc
index a4f9c63142dd95529150a30a70b9c7b5ecd091d7..591280833ca96fd1d933ae96dffd7e2f239bb9d3 100644
--- a/mandoline/ui/browser/browser_manager.cc
+++ b/mandoline/ui/browser/browser_manager.cc
@@ -5,9 +5,12 @@
 #include "mandoline/ui/browser/browser_manager.h"
 
 #include "base/command_line.h"
+#include "base/time/time.h"
 #include "components/view_manager/public/cpp/view.h"
 #include "components/view_manager/public/cpp/view_observer.h"
 #include "mandoline/ui/browser/browser.h"
+#include "mojo/runner/switches.h"
+#include "mojo/services/tracing/tracing.mojom.h"
 
 namespace mandoline {
 
@@ -54,6 +57,24 @@ void BrowserManager::Initialize(mojo::ApplicationImpl* app) {
   // default URL.
   if (browsers_.empty())
     CreateBrowser(GURL(kGoogleURL));
+
+  // Record the browser startup time metrics for performance testing.
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kStatsCollectionController)) {
+    mojo::URLRequestPtr request(mojo::URLRequest::New());
+    request->url = mojo::String::From("mojo:tracing");
+    tracing::StartupPerformanceControllerPtr controller;
+    app_->ConnectToService(request.Pass(), &controller);
+    // TODO(msw): When to record the browser message loop start time?
+    const base::Time startup_time = base::Time::Now();

[yzshen1, 2015/08/13 15:59:12]

Why do we need to call base::Time::Now() three times here? I don't think the
differences between the three are meaningful here.

[msw, 2015/08/14 23:20:35]

This is just a placeholder with TODOs. I'm not entirely sure when/where these
various times should actually be recorded... I can try to figure that out in
this CL, or resolve these TODOs in a follow-up. The repeated Now() calls won't
outlive the TODOs, but I can re-use a single time and leave the TODOS... WDYT?

[yzshen1, 2015/08/17 05:46:38]

SGTM. Thanks!

+    controller->SetBrowserMessageLoopStartTime(startup_time.ToInternalValue());
+    // TODO(msw): When to record the browser window display time?
+    const base::Time display_time = base::Time::Now();
+    controller->SetBrowserWindowDisplayTime(display_time.ToInternalValue());
+    // TODO(msw): When to record the browser open tabs time?
+    const base::Time open_tabs_time = base::Time::Now();
+    controller->SetBrowserOpenTabsTime(open_tabs_time.ToInternalValue());
+  }
 }
 
 bool BrowserManager::ConfigureIncomingConnection(