Ensure that IO thread is not called in last actions by SDCH shutdown

Unregister the sdch_dictionary_fetcher so that it destroys any pending
URLFetcher instances when we are nearing shutdown time.  Dictionaries
are only *potentially* useful (and not needed) for future SDCH 
fetches, so abandoning any pending items is safe and harmless.

b=9669
r=wtc
Review URL: http://codereview.chromium.org/113235

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@16015 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 23 insertions, 2 deletions

diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index a031374..759934b 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -19,6 +19,7 @@
 #include "chrome/browser/google_url_tracker.h"
 #include "chrome/browser/metrics/metrics_service.h"
 #include "chrome/browser/net/dns_global.h"
+#include "chrome/browser/net/sdch_dictionary_fetcher.h"
 #include "chrome/browser/plugin_service.h"
 #include "chrome/browser/profile_manager.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
@@ -143,10 +144,16 @@ BrowserProcessImpl::~BrowserProcessImpl() {
   // this destructor is run.
   automation_provider_list_.reset();
 
+  // We need to shutdown the SdchDictionaryFetcher as it regularly holds
+  // a pointer to a URLFetcher, and that URLFetcher (upon destruction) will do
+  // a PostDelayedTask onto the IO thread.  This shutdown call will both discard
+  // any pending URLFetchers, and avoid creating any more.
+  SdchDictionaryFetcher::Shutdown();
+
   // We need to destroy the MetricsService and GoogleURLTracker before the
   // io_thread_ gets destroyed, since both destructors can call the URLFetcher
-  // destructor, which does an InvokeLater operation on the IO thread.  (The IO
-  // thread will handle that URLFetcher operation before going away.)
+  // destructor, which does an PostDelayedTask operation on the IO thread.  (The
+  // IO thread will handle that URLFetcher operation before going away.)
   metrics_service_.reset();
   google_url_tracker_.reset();
 
diff --git a/chrome/browser/net/sdch_dictionary_fetcher.h b/chrome/browser/net/sdch_dictionary_fetcher.h
index a0a9e2f..e9e092c 100644
--- a/chrome/browser/net/sdch_dictionary_fetcher.h
+++ b/chrome/browser/net/sdch_dictionary_fetcher.h
@@ -31,6 +31,10 @@ class SdchDictionaryFetcher : public URLFetcher::Delegate,
   // SdchManager class with the dictionary's text.
   virtual void Schedule(const GURL& dictionary_url);
 
+  // Stop fetching dictionaries, and abandon any current URLFetcheer operations
+  // so that the IO thread can be stopped.
+  static void Shutdown() { SdchManager::Shutdown(); }
+
  private:
   // Delay in ms between Schedule and actual download.
   // This leaves the URL in a queue, which is de-duped, so that there is less
diff --git a/net/base/sdch_manager.cc b/net/base/sdch_manager.cc
index 30995a8..05b6475 100644
--- a/net/base/sdch_manager.cc
+++ b/net/base/sdch_manager.cc
@@ -82,6 +82,13 @@ SdchManager::~SdchManager() {
 }
 
 // static
+void SdchManager::Shutdown() {
+  if (!global_ )
+    return;
+  global_->fetcher_.reset(NULL);
+}
+
+// static
 void SdchManager::BlacklistDomain(const GURL& url) {
   if (!global_ )
     return;
diff --git a/net/base/sdch_manager.h b/net/base/sdch_manager.h
index e8329e1..43fa484 100644
--- a/net/base/sdch_manager.h
+++ b/net/base/sdch_manager.h
@@ -217,6 +217,9 @@ class SdchManager {
   SdchManager();
   ~SdchManager();
 
+  // Discontinue fetching of dictionaries, as we're now shutting down.
+  static void Shutdown();
+
   // Provide access to the single instance of this class.
   static SdchManager* Global();