Added histograms on process singleton create when remote process exists and we cannot notify it

chrome/browser/process_singleton.h

Index: chrome/browser/process_singleton.h
diff --git a/chrome/browser/process_singleton.h b/chrome/browser/process_singleton.h
index 96a9bf65f42d2cfab301a10573b25739e7e05a4e..a13105ec36e43bde0b2f414ac8f4da09b9d687b6 100644
--- a/chrome/browser/process_singleton.h
+++ b/chrome/browser/process_singleton.h
@@ -49,6 +49,42 @@ class CommandLine;
 
 class ProcessSingleton : public base::NonThreadSafe {
  public:
+  // Used to send the reason of remote hang process termination as histogram.
+  enum RemoteHungProcessTerminateReason {
+#if defined(OS_WIN)
+    USER_ACCEPTED_TERMINATION = 1,
+    NO_VISIBLE_WINDOW_FOUND = 2,
+#elif defined(OS_POSIX)
+    NOTIFY_ATTEMPTS_EXCEEDED = 3,
+    SOCKET_WRITE_FAILED = 4,
+    SOCKET_READ_FAILED = 5,
+#endif
+    REMOTE_HUNG_PROCESS_TERMINATE_REASON_COUNT = 6
+  };
+
+  // Used to send the result of interaction with remote process as histograms in
+  // case when remote process influences on start.
+  enum RemoteProcessInteractionResult {
+    TERMINATE_SUCCEEDED = 0,
+    TERMINATE_FAILED = 1,
+    REMOTE_PROCESS_NOT_FOUND = 2,
+#if defined(OS_WIN)
+    TERMINATE_WAIT_TIMEOUT = 3,
+    RUNNING_PROCESS_NOTIFY_ERROR = 4,
+#elif defined(OS_POSIX)
+    TERMINATE_NOT_ENOUGH_PERMISSIONS = 5,
+    REMOTE_PROCESS_SHUTTING_DOWN = 6,
+    PROFILE_UNLOCKED = 7,
+    PROFILE_UNLOCKED_BEFORE_KILL = 8,
+    SAME_BROWSER_INSTANCE = 9,
+    SAME_BROWSER_INSTANCE_BEFORE_KILL = 10,
+    FAILED_TO_EXTRACT_PID = 11,
+    INVALID_LOCK_FILE = 12,
+    ORPHANED_LOCK_FILE = 13,
+#endif
+    REMOTE_PROCESS_INTERACTION_RESULT_COUNT = 14

[gab, 2017/05/15 16:58:39]

Do not give an explicit number to the count, that way it will grow automatically
if more items are added (and it will also be the appropriate size per platform)

[Alexey Seren, 2017/05/15 19:20:25]

I think that COUNT should have one value on each platform because Bucket count
for histogram is calculated as COUNT + 1
One value of Bucket count for different platforms can be significant for server
that collects and processes this histogram for all platforms.

[gab, 2017/05/15 20:13:05]

AFAIK, UMA doesn't process "count", it's only used client-side to know how many
buckets are required when aggregating the stats.

If this wasn't the case the server would choke when the count changes later and
different versions of chrome report different counts anyways.

In that light, I still insist that we remove the count as it reinforces what you
mentioned which isn't correct in practice.

[Alexey Seren, 2017/05/16 05:30:38]

Acknowledged.
Ok, you are right. Thank you for the explanation!

+  };
+
   // Logged as histograms, do not modify these values.
   enum NotifyResult {
     PROCESS_NONE = 0,
@@ -95,6 +131,7 @@ class ProcessSingleton : public base::NonThreadSafe {
 
 #if defined(OS_POSIX) && !defined(OS_ANDROID)
   static void DisablePromptForTesting();
+  static void SkipIsChromeProcessCheckForTesting();
 #endif
 #if defined(OS_WIN)
   // Called to query whether to kill a hung browser process that has visible