Tracing: Bail out early in tracing tests when tracing is already enabled.

content/browser/tracing/memory_tracing_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 <stdint.h>
 
 #include "base/bind.h"
 #include "base/callback_forward.h"
 #include "base/command_line.h"
 #include "base/run_loop.h"
@@ skipping 92 matching lines @@
   }
 
   void TearDown() override {
     MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
         mock_dump_provider_.get());
     mock_dump_provider_.reset();
     ContentBrowserTest::TearDown();
   }
 
   void EnableMemoryTracing() {
-    CHECK(!base::trace_event::TraceLog::GetInstance()->IsEnabled())
-        << "Tracing seems to be already enabled. Very likely this is because "
-           "the startup tracing file has been leaked from a previous test.";
+    // Re-enabling tracing could crash these tests https://crbug.com/657628 .
+    if (base::trace_event::TraceLog::GetInstance()->IsEnabled()) {
+      FAIL() << "Tracing seems to be already enabled. "
+                "Very likely this is because the startup tracing file "
+                "has been leaked from a previous test.";
+    }
     // Enable tracing without periodic dumps.
     base::trace_event::TraceConfig trace_config(
         base::trace_event::TraceConfigMemoryTestUtil::
             GetTraceConfig_EmptyTriggers());
 
     base::RunLoop run_loop;
     bool success = TracingController::GetInstance()->StartTracing(
       trace_config, run_loop.QuitClosure());
     EXPECT_TRUE(success);
     run_loop.Run();
@@ skipping 187 matching lines @@
   EXPECT_CALL(*this, OnMemoryDumpDone(_, true /* success */));
 
   EnableMemoryTracing();
   RequestGlobalDumpAndWait(false /* from_renderer_thread */,
                            MemoryDumpType::EXPLICITLY_TRIGGERED,
                            MemoryDumpLevelOfDetail::DETAILED);
   DisableTracing();
 }
 
 }  // namespace content