Revert 150969 - Disable getting histogram data from child processes other than...

Revert 150969 - Disable getting histogram data from child processes other than the renderer processes.
Store the histogram name in the local variable for debugging purposes when we crash.

R=jar
TBR=jam
BUG=140688
TEST=base (histogram unit tests) and unit_tests.
Review URL: https://chromiumcodereview.appspot.com/10831247

TBR=rtenneti@google.com
Review URL: https://chromiumcodereview.appspot.com/10865002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@152427 0039d316-1c4b-4281-b951-d872f2087c98

base/metrics/histogram_snapshot_manager.cc

@@ -4,10 +4,7 @@
 
 #include "base/metrics/histogram_snapshot_manager.h"
 
-#include "base/compiler_specific.h"
-#include "base/debug/alias.h"
 #include "base/metrics/statistics_recorder.h"
-#include "base/string_util.h"
 
 using base::Histogram;
 using base::StatisticsRecorder;
@@ -47,12 +44,6 @@ void HistogramSnapshotManager::PrepareDelta(const Histogram& histogram) {
 
   int corruption = histogram.FindCorruption(snapshot);
 
-  char histogram_name_buf[128];
-  base::strlcpy(histogram_name_buf,
-                histogram_name.c_str(),
-                arraysize(histogram_name_buf));
-  base::debug::Alias(histogram_name_buf);
-
   // Crash if we detect that our histograms have been overwritten.  This may be
   // a fair distance from the memory smasher, but we hope to correlate these
   // crashes with other events, such as plugins, or usage patterns, etc.

content/browser/histogram_controller.cc

@@ -70,13 +70,11 @@ void HistogramController::GetHistogramDataFromChildProcesses(
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   int pending_processes = 0;
-  /* TODO(rtenneti): Enable collecting histogram from child processes.
   for (BrowserChildProcessHostIterator iter; !iter.Done(); ++iter) {
     ++pending_processes;
     if (!iter.Send(new ChildProcessMsg_GetChildHistogramData(sequence_number)))
       --pending_processes;
   }
-  */
 
   BrowserThread::PostTask(
       BrowserThread::UI,