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..9a9694be9f0e056f3aa0d3d51f239c968ffaaf67 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"
@@ -24,6 +25,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/version.h"
 #include "chrome/browser/browser_process.h"
 #import "chrome/browser/mac/dock.h"
 #include "chrome/browser/browser_process.h"
@@ -57,6 +59,11 @@ 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, we record the version of the app shim.
+// This is the number of buckets in the UMA histogram, i.e. the highest version
+// we can track plus 1.
+const int kAppShimErrorVersionMax = 51;

[Robert Sesek, 2014/07/02 14:53:51]

FYI Chrome 51 will ship in December 2015/January 2016, assuming we stay on the
current six week schedule ;-).

+
 class ScopedCarbonHandle {
  public:
   ScopedCarbonHandle(size_t initial_size) : handle_(NewHandle(initial_size)) {
@@ -496,6 +503,21 @@ web_app::ShortcutInfo BuildShortcutInfoFromBundle(
   return shortcut_info;
 }
 
+web_app::ShortcutInfo RecordAppShimErrorAndBuildShortcutInfo(
+    const base::FilePath& bundle_path) {
+  NSDictionary* plist = ReadPlist(GetPlistPath(bundle_path));
+  base::Version full_version(base::SysNSStringToUTF8(
+      [plist valueForKey:app_mode::kCFBundleShortVersionStringKey]));
+  int major_version = 0;
+  if (full_version.IsValid())
+    major_version = full_version.components()[0];
+  UMA_HISTOGRAM_ENUMERATION("Apps.AppShimErrorVersion",
+                            major_version,
+                            kAppShimErrorVersionMax);

[Alexei Svitkine (slow), 2014/07/04 12:49:24]

I suggest using UMA_HISTOGRAM_SPARSE_SLOWLY() instead, then you don't need to
have kAppShimErrorVersionMax and your histogram wouldn't be using memory for 51
buckets that are mostly empty.

[jackhou1, 2014/07/07 05:38:36]

Done.

+
+  return BuildShortcutInfoFromBundle(bundle_path);
+}
+
 void UpdateFileTypes(NSMutableDictionary* plist,
                      const extensions::FileHandlersInfo& file_handlers_info) {
   NSMutableArray* document_types =
@@ -939,7 +961,7 @@ 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;