Support parallel captures from the StackSamplingProfiler.

base/threading/thread_restrictions.h

Index: base/threading/thread_restrictions.h
diff --git a/base/threading/thread_restrictions.h b/base/threading/thread_restrictions.h
index 97f3eb6129e108637a2d4de68e9f36ad1e386260..1b51c46d91a11d53e11e703f21a7169b3c99a829 100644
--- a/base/threading/thread_restrictions.h
+++ b/base/threading/thread_restrictions.h
@@ -99,6 +99,7 @@ class TaskTracker;
 
 class SequencedWorkerPool;
 class SimpleThread;
+class StackSamplingProfiler;
 class Thread;
 class ThreadTestHelper;
 
@@ -183,6 +184,7 @@ class BASE_EXPORT ThreadRestrictions {
   // BEGIN ALLOWED USAGE.
   friend class android_webview::AwFormDatabaseService;
   friend class android_webview::CookieManager;
+  friend class base::StackSamplingProfiler;
   friend class content::BrowserShutdownProfileDumper;
   friend class content::BrowserSurfaceViewManager;
   friend class content::BrowserTestBase;