Send Chrome's process id to the app shim.

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 3811329ec704d1c7f99b4e2607794afdcb80fdcb..c7ee57b9a514dd2d29b169c81425a00c22f1305e 100644
--- a/chrome/browser/web_applications/web_app_mac.mm
+++ b/chrome/browser/web_applications/web_app_mac.mm
@@ -17,8 +17,10 @@
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/path_service.h"
+#include "base/process/process.h"
 #include "base/strings/string_util.h"
 #include "base/strings/string16.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #import "chrome/browser/mac/dock.h"
@@ -211,6 +213,9 @@ void LaunchShimOnFileThread(
 
   CommandLine command_line(CommandLine::NO_PROGRAM);
   command_line.AppendSwitch(app_mode::kNoLaunchApp);
+  command_line.AppendSwitchASCII(
+      app_mode::kChromeProcessId,
+      base::IntToString(base::Process::Current().pid()));
   // Launch without activating (kLSLaunchDontSwitch).
   base::mac::OpenApplicationWithPath(
       shim_path, command_line, kLSLaunchDefaults | kLSLaunchDontSwitch, NULL);