Have content/ create and destroy its own threads.

content/public/browser/browser_main_parts.h

Index: content/public/browser/browser_main_parts.h
diff --git a/content/public/browser/browser_main_parts.h b/content/public/browser/browser_main_parts.h
index 860541c4e14f6905585e9a2afc56634ca21983bc..15721c57f57e79f75682e2cc30b6d4d145ecbdc0 100644
--- a/content/public/browser/browser_main_parts.h
+++ b/content/public/browser/browser_main_parts.h
@@ -8,6 +8,7 @@
 
 #include "base/basictypes.h"
 #include "content/common/content_export.h"
+#include "content/public/browser/browser_thread.h"
 
 namespace content {
 
@@ -64,15 +65,32 @@ class CONTENT_EXPORT BrowserMainParts {
   // Allows an embedder to do any extra toolkit initialization.
   virtual void ToolkitInitialized() = 0;
 
+  // Child threads have not been created at this point.
   virtual void PreMainMessageLoopRun() = 0;
 
+  // The various browser threads have been created at this point.
+  virtual void PreMainMessageLoopRunThreadsCreated() = 0;
+
   // Returns true if the message loop was run, false otherwise.
   // If this returns false, the default implementation will be run.
   // May set |result_code|, which will be returned by |BrowserMain()|.
   virtual bool MainMessageLoopRun(int* result_code) = 0;
 
+  // This happens after the main message loop has stopped, but before
+  // threads are stopped.
   virtual void PostMainMessageLoopRun() = 0;
 
+  // Called once for each thread owned by the content framework just
+  // before and just after it is torn down. This is in reverse order
+  // of the threads' appearance in the BrowserThread::ID enumeration.
+  // Note that you will not receive such a call for BrowserThread::UI,
+  // since it is the main thread of the application.
+  virtual void PreStopThread(BrowserThread::ID identifier) = 0;
+  virtual void PostStopThread(BrowserThread::ID identifier) = 0;
+
+  // Called as the very last part of shutdown.
+  virtual void FinalCleanup() = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(BrowserMainParts);
 };