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

chrome/browser/memory_details.h

Index: chrome/browser/memory_details.h
diff --git a/chrome/browser/memory_details.h b/chrome/browser/memory_details.h
index 568f591328a4af632411c6d058119e1e8db94596..422a09bc07e7fd88ee885bbcfb48b60ce9c39a92 100644
--- a/chrome/browser/memory_details.h
+++ b/chrome/browser/memory_details.h
@@ -107,6 +107,11 @@ class ProcessInfoSnapshot;
 //    }
 class MemoryDetails : public base::RefCountedThreadSafe<MemoryDetails> {
  public:
+  enum UserMetricsMode {
+    UPDATE_USER_METRICS,  // Update UMA memory histograms with results.
+    SKIP_USER_METRICS
+  };
+
   // Constructor.
   MemoryDetails();
 
@@ -116,10 +121,15 @@ class MemoryDetails : public base::RefCountedThreadSafe<MemoryDetails> {
 
   // 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>;
@@ -156,8 +166,7 @@ class MemoryDetails : public base::RefCountedThreadSafe<MemoryDetails> {
   // 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.
@@ -165,6 +174,8 @@ class MemoryDetails : public base::RefCountedThreadSafe<MemoryDetails> {
 
   std::vector<ProcessData> process_data_;
 
+  UserMetricsMode user_metrics_mode_;
+
   DISALLOW_COPY_AND_ASSIGN(MemoryDetails);
 };