Re-enable two flaky tests that were disabled due to timeouts.

chrome/browser/image_decoder_browsertest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/image_decoder.h"
 
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "chrome/grit/generated_resources.h"
 #include "chrome/test/base/in_process_browser_test.h"
@@ skipping 225 matching lines @@
   test_request.reset();
   runner->Run();
 }
 
 // Killing the utility process counts as a crash. Thus the request fails.
 // If ImageDecoder did not handle the crash properly, the request never finishes
 // and this test would hang.
 // Note: This test is inherently racy because KillProcessObserver lives on the
 // UI thread but ImageDecoder does its work mainly on the IO thread. So the test
 // checks for both possible valid outcomes.
-//
-// Flaky timeouts on Linux ASan / LSan, and on Mac. crbug.com/618206
-#if (defined(ADDRESS_SANITIZER) || defined(LEAK_SANITIZER)) && defined(OS_LINUX)
-#define MAYBE_StartAndKillProcess DISABLED_StartAndKillProcess
-#elif defined(OS_MACOSX)
-#define MAYBE_StartAndKillProcess DISABLED_StartAndKillProcess
-#else
-#define MAYBE_StartAndKillProcess StartAndKillProcess
-#endif
-IN_PROC_BROWSER_TEST_F(ImageDecoderBrowserTest, MAYBE_StartAndKillProcess) {
+IN_PROC_BROWSER_TEST_F(ImageDecoderBrowserTest, StartAndKillProcess) {
   KillProcessObserver observer;
   scoped_refptr<content::MessageLoopRunner> runner =
       new content::MessageLoopRunner;
   TestImageRequest test_request(runner->QuitClosure());
   ImageDecoder::Start(&test_request, GetValidPngString());
   runner->Run();
   if (!test_request.decode_succeeded()) {
     // The UI thread won the race. Make sure the utility process did get killed.
     EXPECT_TRUE(observer.did_kill());
   }
   // Else the IO thread won the race and the image got decoded. Oh well.
 }