Automatically adapt to faster/slower uploads of renderer histograms

This replaces the current time based approach (chrome is given N seconds
to upload all renederer histograms) with an asynch callback approach
that waits until all renderers have responded (with their updates). It
uses a fall-back timer to ensure that a hung renderer won't delay things
forever as well.

This causes faster (and complete) updates in about:histograms as well
as generally assuring complete updates during UMA gatherings.

This code was contributed by Raman Tenneti in CL 42496
http://codereview.chromium.org/42496

bug=12850

r=raman
Review URL: http://codereview.chromium.org/113473

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@17123 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 10 insertions, 8 deletions

diff --git a/chrome/browser/browser_about_handler.cc b/chrome/browser/browser_about_handler.cc
index 6c46f18..f699b1e 100644
--- a/chrome/browser/browser_about_handler.cc
+++ b/chrome/browser/browser_about_handler.cc
@@ -24,6 +24,7 @@
 #include "chrome/browser/net/dns_global.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
+#include "chrome/common/histogram_synchronizer.h"
 #include "chrome/common/jstemplate_builder.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/pref_service.h"
@@ -45,6 +46,9 @@
 #include "chrome/browser/views/about_network_dialog.h"
 #endif
 
+using base::Time;
+using base::TimeDelta;
+
 namespace {
 
 // The paths used for the about pages.
@@ -137,16 +141,14 @@ std::string AboutDns() {
 }
 
 std::string AboutHistograms(const std::string& query) {
-  std::string data;
-  for (RenderProcessHost::iterator it = RenderProcessHost::begin();
-       it != RenderProcessHost::end(); ++it) {
-    it->second->Send(new ViewMsg_GetRendererHistograms());
-  }
+  TimeDelta wait_time = TimeDelta::FromMilliseconds(10000);
 
-  // TODO(raman): Delay page layout until we get respnoses
-  // back from renderers, and not have to use a fixed size delay.
-  PlatformThread::Sleep(1000);
+  HistogramSynchronizer* current_synchronizer =
+      HistogramSynchronizer::CurrentSynchronizer();
+  DCHECK(current_synchronizer != NULL);
+  current_synchronizer->FetchRendererHistogramsSynchronously(wait_time);
 
+  std::string data;
   StatisticsRecorder::WriteHTMLGraph(query, &data);
   return data;
 }