cros: Log per-process memory use on low memory events

chrome/browser/memory_details.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_MEMORY_DETAILS_H_
 #define CHROME_BROWSER_MEMORY_DETAILS_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 89 matching lines @@
 //      }
 //
 //      // Your other class stuff here
 //
 //      virtual void OnDetailsAvailable() {
 //        // do work with memory info here
 //      }
 //    }
 class MemoryDetails : public base::RefCountedThreadSafe<MemoryDetails> {
  public:
+  enum UserMetricsMode {
+    UPDATE_USER_METRICS,  // Update UMA memory histograms with results.
+    SKIP_USER_METRICS
+  };
+
   // Constructor.
   MemoryDetails();
 
   // Access to the process detail information.  This data is only available
   // after OnDetailsAvailable() has been called.
   const std::vector<ProcessData>& processes() { return process_data_; }
 
   // Initiate updating the current memory details.  These are fetched
   // asynchronously because data must be collected from multiple threads.
+  // Updates UMA memory histograms if |mode| is UPDATE_USER_METRICS.
   // OnDetailsAvailable will be called when this process is complete.
-  void StartFetch();
+  void StartFetch(UserMetricsMode user_metrics_mode);
 
-  virtual void OnDetailsAvailable() {}
+  virtual void OnDetailsAvailable() = 0;
+
+  // Returns a string summarizing memory usage of the Chrome browser process
+  // and all sub-processes, suitable for logging.
+  std::string ToLogString();
 
  protected:
   friend class base::RefCountedThreadSafe<MemoryDetails>;
 
   virtual ~MemoryDetails();
 
  private:
   // Collect child process information on the IO thread.  This is needed because
   // information about some child process types (i.e. plugins) can only be taken
   // on that thread.  The data will be used by about:memory.  When finished,
@@ skipping 16 matching lines @@
   void CollectProcessDataChrome(
       const std::vector<ProcessMemoryInformation>& child_info,
       base::ProcessId pid,
       const ProcessInfoSnapshot& process_info);
 #endif
 
   // Collect child process information on the UI thread.  Information about
   // renderer processes is only available there.
   void CollectChildInfoOnUIThread();
 
-  // Each time we take a memory sample, we do a little work to update
-  // the global histograms for tracking memory usage.
+  // Updates the global histograms for tracking memory usage.
   void UpdateHistograms();
 
   // Returns a pointer to the ProcessData structure for Chrome.
   ProcessData* ChromeBrowser();
 
   std::vector<ProcessData> process_data_;
 
+  UserMetricsMode user_metrics_mode_;
+
   DISALLOW_COPY_AND_ASSIGN(MemoryDetails);
 };
 
 #endif  // CHROME_BROWSER_MEMORY_DETAILS_H_