Disable UpdateProcessPriority() on startup by default.

chrome/browser/renderer_host/render_process_host_chrome_browsertest.cc

 // Copyright (c) 2012 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 "base/command_line.h"
 #include "base/macros.h"
 #include "base/path_service.h"
 #include "base/process/process.h"
 #include "base/test/test_timeouts.h"
 #include "build/build_config.h"
@@ skipping 318 matching lines @@
 
   // Load another tab in background. The renderer of the new tab should be
   // backgrounded, while visibility of the other renderers should not change.
   GURL page3("data:text/html,hello world3");
   base::Process process3 = OpenBackgroundTab(page3);
   ASSERT_TRUE(process3.IsValid());
   EXPECT_NE(process3.Pid(), process1.Pid());
   EXPECT_NE(process3.Pid(), process2.Pid());
   EXPECT_TRUE(process1.IsProcessBackgrounded());
   EXPECT_FALSE(process2.IsProcessBackgrounded());
-  EXPECT_TRUE(process3.IsProcessBackgrounded());
+  // TODO(gab): The new background tab should be backgrounded but it currently
+  // intentionally isn't per a workaround to https://crbug.com/560446 in
+  // RenderProcessHostImpl::OnProcessLaunched().
+  EXPECT_FALSE(process3.IsProcessBackgrounded());
 
   // Navigate back to the first page. Its renderer should be in foreground
   // again while the other renderers should be backgrounded.
   EXPECT_EQ(process1.Pid(), ShowSingletonTab(page1).Pid());
   EXPECT_FALSE(process1.IsProcessBackgrounded());
   EXPECT_TRUE(process2.IsProcessBackgrounded());
+  // TODO(gab): Same as above.
+  EXPECT_FALSE(process3.IsProcessBackgrounded());
+
+  // TODO(gab): Remove this when https://crbug.com/560446 is fixed, but for now
+  // confirm that the correct state is at least achieved when tab #3 is
+  // explicitly foregrounded and re-backgrounded.
+  EXPECT_EQ(process3.Pid(), ShowSingletonTab(page3).Pid());
+  EXPECT_EQ(process1.Pid(), ShowSingletonTab(page1).Pid());
+  EXPECT_FALSE(process1.IsProcessBackgrounded());
+  EXPECT_TRUE(process2.IsProcessBackgrounded());
   EXPECT_TRUE(process3.IsProcessBackgrounded());
 }
 #endif
 
 // TODO(nasko): crbug.com/173137
 // Disable on Mac 10.9 due to ongoing flakiness. (crbug.com/442785)
 #if defined(OS_MACOSX)
 #define MAYBE_ProcessOverflow DISABLED_ProcessOverflow
 #else
 #define MAYBE_ProcessOverflow ProcessOverflow
@@ skipping 317 matching lines @@
       content::ExecuteScript(audio_tab_web_contents_,
                              "document.getElementById('audioPlayer').play();"));
 
   // Wait until the two pages are not backgrounded.
   while (no_audio_process_.IsProcessBackgrounded() ||
          audio_process_.IsProcessBackgrounded()) {
     base::RunLoop().RunUntilIdle();
     base::PlatformThread::Sleep(TestTimeouts::tiny_timeout());
   }
 }