Add UMA for --app-shim-error.

chrome/browser/web_applications/web_app_mac.mm

Index: chrome/browser/web_applications/web_app_mac.mm
diff --git a/chrome/browser/web_applications/web_app_mac.mm b/chrome/browser/web_applications/web_app_mac.mm
index 02f3f0dc7c14ead4c29c6e2e6b3ff23c5122760f..862c19f1e67aa4404cdf26a43c4b92085649d614 100644
--- a/chrome/browser/web_applications/web_app_mac.mm
+++ b/chrome/browser/web_applications/web_app_mac.mm
@@ -16,6 +16,7 @@
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/mac/scoped_nsobject.h"
+#include "base/metrics/histogram.h"
 #include "base/path_service.h"
 #include "base/process/process_handle.h"
 #include "base/strings/string16.h"
@@ -57,6 +58,17 @@ namespace {
 // Launch Services Key to run as an agent app, which doesn't launch in the dock.
 NSString* const kLSUIElement = @"LSUIElement";
 
+// When a --app-shim-error is triggered, this is used to record the version of
+// the app shim. These are chosen to track the change from 32-bit to 64-bit.
+// Order must be maintained as this is used in UMA.
+enum AppShimError {
+  APP_SHIM_ERROR_UNKNOWN,
+  APP_SHIM_ERROR_37_OR_LOWER,
+  APP_SHIM_ERROR_38,
+  APP_SHIM_ERROR_39_OR_HIGHER,
+  APP_SHIM_ERROR_COUNT,
+};
+
 class ScopedCarbonHandle {
  public:
   ScopedCarbonHandle(size_t initial_size) : handle_(NewHandle(initial_size)) {
@@ -496,6 +508,27 @@ web_app::ShortcutInfo BuildShortcutInfoFromBundle(
   return shortcut_info;
 }
 
+web_app::ShortcutInfo RecordAppShimErrorAndBuildShortcutInfo(
+    const base::FilePath& bundle_path) {
+  NSDictionary* plist = ReadPlist(GetPlistPath(bundle_path));
+  int version = [[[[plist valueForKey:app_mode::kCFBundleShortVersionStringKey]

[Robert Sesek, 2014/07/01 14:10:39]

May want to use base/version.h.

[jackhou1, 2014/07/02 03:18:12]

Done.

+      componentsSeparatedByString:@"."] objectAtIndex:0] intValue];
+  AppShimError error_enum;
+  if (version < 38)

[tapted, 2014/07/01 12:48:11]

probably needs `version > 0 &&..` here so the unknown case can be caught

[jackhou1, 2014/07/02 03:18:12]

Done.

+    error_enum = APP_SHIM_ERROR_37_OR_LOWER;
+  else if (version == 38)
+    error_enum = APP_SHIM_ERROR_38;
+  else if (version > 38)
+    error_enum = APP_SHIM_ERROR_39_OR_HIGHER;
+  else
+    error_enum = APP_SHIM_ERROR_UNKNOWN;
+  UMA_HISTOGRAM_ENUMERATION("Apps.AppShimError",

[Robert Sesek, 2014/07/01 14:10:39]

Would it make more sense to just histogram the |version| with a linear scale?

[jackhou1, 2014/07/02 03:18:11]

Done.

+                            error_enum,
+                            APP_SHIM_ERROR_COUNT);
+
+  return BuildShortcutInfoFromBundle(bundle_path);
+}
+
 void UpdateFileTypes(NSMutableDictionary* plist,
                      const extensions::FileHandlersInfo& file_handlers_info) {
   NSMutableArray* document_types =
@@ -939,7 +972,7 @@ bool MaybeRebuildShortcut(const CommandLine& command_line) {
   base::PostTaskAndReplyWithResult(
       content::BrowserThread::GetBlockingPool(),
       FROM_HERE,
-      base::Bind(&BuildShortcutInfoFromBundle,
+      base::Bind(&RecordAppShimErrorAndBuildShortcutInfo,
                  command_line.GetSwitchValuePath(app_mode::kAppShimError)),
       base::Bind(&RebuildAppAndLaunch));
   return true;