[Mac] Re-enable AppShimInteractiveTest.Launch.

The stack trace suggests LSOpenApplication fails to find the shim, and this
happens after waiting on a run loop. So a likely cause is that we're not
successfully waiting for the file operations to finish.

This CL changes the test to observe the parent directory instead of the shim
directory, and adds checks that the path exists before proceeding. If the test
still fails for this reason, at least it'll say so.

BUG=415422

Review URL: https://codereview.chromium.org/598443002

Cr-Commit-Position: refs/heads/master@{#296185}

apps/app_shim/app_shim_interactive_uitest_mac.mm

@@ -53,11 +53,12 @@ class AppShimInteractiveTest : public extensions::PlatformAppBrowserTest {
 class WindowedFilePathWatcher
     : public base::RefCountedThreadSafe<WindowedFilePathWatcher> {
  public:
-  WindowedFilePathWatcher(const base::FilePath& path) : observed_(false) {
+  WindowedFilePathWatcher(const base::FilePath& path)
+      : path_(path), observed_(false) {
     content::BrowserThread::PostTask(
         content::BrowserThread::FILE,
         FROM_HERE,
-        base::Bind(&WindowedFilePathWatcher::Watch, this, path));
+        base::Bind(&WindowedFilePathWatcher::Watch, this));
   }
 
   void Wait() {
@@ -72,16 +73,22 @@ class WindowedFilePathWatcher
   friend class base::RefCountedThreadSafe<WindowedFilePathWatcher>;
   virtual ~WindowedFilePathWatcher() {}
 
-  void Watch(const base::FilePath& path) {
-    watcher_.Watch(
-        path, false, base::Bind(&WindowedFilePathWatcher::Observe, this));
+  void Watch() {
+    watcher_.reset(new base::FilePathWatcher);
+    watcher_->Watch(path_.DirName(),
+                    false,
+                    base::Bind(&WindowedFilePathWatcher::Observe, this));
   }
 
   void Observe(const base::FilePath& path, bool error) {
-    content::BrowserThread::PostTask(
-        content::BrowserThread::UI,
-        FROM_HERE,
-        base::Bind(&WindowedFilePathWatcher::StopRunLoop, this));
+    DCHECK(!error);
+    if (base::PathExists(path_)) {
+      watcher_.reset();
+      content::BrowserThread::PostTask(
+          content::BrowserThread::UI,
+          FROM_HERE,
+          base::Bind(&WindowedFilePathWatcher::StopRunLoop, this));
+    }
   }
 
   void StopRunLoop() {
@@ -91,7 +98,8 @@ class WindowedFilePathWatcher
   }
 
  private:
-  base::FilePathWatcher watcher_;
+  const base::FilePath path_;
+  scoped_ptr<base::FilePathWatcher> watcher_;
   bool observed_;
   scoped_ptr<base::RunLoop> run_loop_;
 
@@ -214,8 +222,7 @@ bool HasAppShimHost(Profile* profile, const std::string& app_id) {
 namespace apps {
 
 // Shims require static libraries http://crbug.com/386024.
-// This test is flaky on OSX. http://crbug.com/415422
-#if defined(COMPONENT_BUILD) || defined(OS_MACOSX)
+#if defined(COMPONENT_BUILD)
 #define MAYBE_Launch DISABLED_Launch
 #define MAYBE_RebuildShim DISABLED_RebuildShim
 #else
@@ -247,6 +254,7 @@ IN_PROC_BROWSER_TEST_F(AppShimInteractiveTest, MAYBE_Launch) {
       new WindowedFilePathWatcher(shim_path);
   web_app::UpdateAllShortcuts(base::string16(), profile(), app);
   file_watcher->Wait();
+  ASSERT_TRUE(base::PathExists(shim_path));
   NSString* bundle_id = GetBundleID(shim_path);
 
   // Case 1: Launch the shim, it should start the app.