Disable UpdateProcessPriority() on startup by default.

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 2536 matching lines @@
   if (child_process_launcher_) {
     DCHECK(child_process_launcher_->GetProcess().IsValid());
     DCHECK(!is_process_backgrounded_);
 
     // Not all platforms launch processes in the same backgrounded state. Make
     // sure |is_process_backgrounded_| reflects this platform's initial process
     // state.
     is_process_backgrounded_ =
         child_process_launcher_->GetProcess().IsProcessBackgrounded();
 
-#if defined(OS_WIN)
-    // Experiment with not setting the initial priority of a renderer, as this
-    // might be a visible tab but since no widgets are currently present, it
-    // will get backgrounded. See https://crbug.com/560446.
-    if (base::FeatureList::IsEnabled(
-            features::kUpdateRendererPriorityOnStartup)) {
-      UpdateProcessPriority();
-    }
-#else
+    // Disable updating process priority on startup for now as it incorrectly
+    // results in backgrounding foreground navigations until their first commit
+    // is made. A better long term solution would be to be aware of the tab's
+    // visibility at this point. https://crbug.com/560446.
+    // Except on Android for now because of https://crbug.com/601184 :-(.
+#if defined(OS_ANDROID)
     UpdateProcessPriority();
 #endif
   }
 
   // NOTE: This needs to be before sending queued messages because
   // ExtensionService uses this notification to initialize the renderer process
   // with state that must be there before any JavaScript executes.
   //
   // The queued messages contain such things as "navigate". If this notification
   // was after, we can end up executing JavaScript before the initialization
@@ skipping 215 matching lines @@
 
     // Skip widgets in other processes.
     if (rvh->GetProcess()->GetID() != GetID())
       continue;
 
     rvh->OnWebkitPreferencesChanged();
   }
 }
 
 }  // namespace content