Fix stack symbolization in Telemetry on Windows.

chrome/app/chrome_crash_reporter_client.cc

Index: chrome/app/chrome_crash_reporter_client.cc
diff --git a/chrome/app/chrome_crash_reporter_client.cc b/chrome/app/chrome_crash_reporter_client.cc
index deec30509c77abc223cfbb55320259a7f9c4a3e7..f66fa98a592825f69e4baae767668058236ccea3 100644
--- a/chrome/app/chrome_crash_reporter_client.cc
+++ b/chrome/app/chrome_crash_reporter_client.cc
@@ -282,11 +282,6 @@ base::FilePath ChromeCrashReporterClient::GetReporterLogFilename() {
 
 bool ChromeCrashReporterClient::GetCrashDumpLocation(
     base::FilePath* crash_dir) {
-#if defined(OS_WIN)
-  // TODO(scottmg): Consider supporting --user-data-dir. See
-  // https://crbug.com/565446.
-  return chrome::GetDefaultCrashDumpLocation(crash_dir);
-#else
   // By setting the BREAKPAD_DUMP_LOCATION environment variable, an alternate
   // location to write breakpad crash dumps can be set.
   scoped_ptr<base::Environment> env(base::Environment::Create());
@@ -294,9 +289,22 @@ bool ChromeCrashReporterClient::GetCrashDumpLocation(
   if (env->GetVar("BREAKPAD_DUMP_LOCATION", &alternate_crash_dump_location)) {
     base::FilePath crash_dumps_dir_path =
         base::FilePath::FromUTF8Unsafe(alternate_crash_dump_location);
+
+#if defined(OS_WIN)
+    // If this environment variable exists, then for the time being,
+    // short-circuit how it's handled on Windows.
+    *crash_dir = crash_dumps_dir_path;

[scottmg, 2016/04/04 19:22:02]

Is this directory guaranteed to exist? PathService::Override() creates.

[Ken Russell (switch to Gerrit), 2016/04/04 20:26:44]

Not currently guaranteed by this code, no.

The current user (Telemetry) does guarantee that it exists.

Looking back at earlier CLs, it seemed that PathService::Override couldn't be
used yet for this purpose, for reasons I didn't understand -- is that still
true?

[scottmg, 2016/04/04 21:04:58]

I don't think PathService can be used, in general, no. (Because Crashpad is
initialized before PathService is, to catch early crashes).

[Ken Russell (switch to Gerrit), 2016/04/04 21:59:25]

OK. Can we proceed with this change as written then? It basically just honors
the environment variable setting on Windows, expecting the user to have made the
directory.

[scottmg, 2016/04/04 22:12:04]

OK, lgtm with a comment saying why we need to (telemetry) and that it has to be
BREAKPAD_... for reason X with a link to something or other.

+    return true;
+#else
     PathService::Override(chrome::DIR_CRASH_DUMPS, crash_dumps_dir_path);
+#endif
   }
 
+#if defined(OS_WIN)
+  // TODO(scottmg): Consider supporting --user-data-dir. See
+  // https://crbug.com/565446.
+  return chrome::GetDefaultCrashDumpLocation(crash_dir);
+#else
   return PathService::Get(chrome::DIR_CRASH_DUMPS, crash_dir);
 #endif
 }