[TaskScheduler]: Migrate off of ScopedAllowWait in /base/android/java_handler_thread.cc

base::ThreadRestrictions::ScopedAllowWait is deprecated in favor of its more
explicit counterpart.

It should have been replaced by :
 * base::ScopedAllowBaseSyncPrimitivesForTesting in test files.
 * base::ScopedAllowBaseSyncPrimitives in non-test files
 * base::ScopedAllowBaseSyncPrimitivesOutsideBlockingScope when it's used on threads
   that don't allow blocking
The last one is strongly frowned upon but this CL aims to document existing
behavior rather than address it. Owners are encouraged to follow-up by fixing
unnecessary waits and more particularly unnecessary waits
outside-blocking-scope.

Note: The non-for-testing versions require friend'ing in thread_restrictions.h
but care was taken to add these friends ahead of git cl split (since it wasn't
possible to do a line-by-line associated CL split).
Refer to the top-level CL if necessary :
https://chromium-review.googlesource.com/c/chromium/src/+/1288533

Please CQ if LGTY!

This CL was uploaded by git cl split.

R=rmcilroy@chromium.org

Bug: 766678
Change-Id: Ibed489dd8ea6d845199f91081f3e986f3014cf67
Reviewed-on: https://chromium-review.googlesource.com/c/1325196
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608817}

base/android/java_handler_thread.cc

@@ -65,7 +65,7 @@ void JavaHandlerThread::Start() {
       reinterpret_cast<intptr_t>(&initialize_event));
   // Wait for thread to be initialized so it is ready to be used when Start
   // returns.
-  base::ThreadRestrictions::ScopedAllowWait wait_allowed;
+  base::ScopedAllowBaseSyncPrimitivesOutsideBlockingScope wait_allowed;
   initialize_event.Wait();
 }
 

base/threading/thread_restrictions.h

@@ -342,7 +342,6 @@ class BASE_EXPORT ScopedAllowBaseSyncPrimitives {
   // Allowed usage:
   friend class ::BrowserProcessImpl;
   friend class SimpleThread;
-  friend class android::JavaHandlerThread;
   friend class android_webview::AwFormDatabaseService;
   friend class android_webview::CookieManager;
   friend class base::GetAppOutputScopedAllowBaseSyncPrimitives;
@@ -394,6 +393,7 @@ class BASE_EXPORT ScopedAllowBaseSyncPrimitivesOutsideBlockingScope {
 
   // Allowed usage:
   friend class ::KeyStorageLinux;
+  friend class android::JavaHandlerThread;
   friend class Thread;
   friend class base::MessageLoopImpl;
   friend class content::ScopedAllowWaitForDebugURL;