Add method to unregister mailto: handler

The implementation of mailto: handler observes the SyncService
so it needs to unregister itself during shutdown. Add a method
called during application shutdown to unregister the handler.

Bug: 854159
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I99e6de4f488ef6ef0fe7cd7f48deece648051503
Reviewed-on: https://chromium-review.googlesource.com/1106161
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568789}

ios/chrome/app/main_controller.mm

@@ -958,6 +958,10 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
 
   [_mainCoordinator stop];
 
+  ios::GetChromeBrowserProvider()
+      ->GetMailtoHandlerProvider()
+      ->RemoveMailtoHandling();
+
   _chromeMain.reset();
 }
 
@@ -1152,14 +1156,13 @@ void MainControllerAuthenticationServiceDelegate::ClearBrowsingData(
         enqueueBlockNamed:kMailtoHandlingInitialization
                     block:^{
                       __strong __typeof(weakSelf) strongSelf = weakSelf;
-                      if (!strongSelf) {
+                      if (!strongSelf || !strongSelf->_mainBrowserState) {
                         return;
                       }
-                      MailtoHandlerProvider* provider =
-                          ios::GetChromeBrowserProvider()
-                              ->GetMailtoHandlerProvider();
-                      provider->PrepareMailtoHandling(
-                          strongSelf->_mainBrowserState);
+                      ios::GetChromeBrowserProvider()
+                          ->GetMailtoHandlerProvider()
+                          ->PrepareMailtoHandling(
+                              strongSelf->_mainBrowserState);
                     }];
   }
 }

ios/public/provider/chrome/browser/mailto/mailto_handler_provider.h

@@ -23,8 +23,11 @@ class MailtoHandlerProvider {
   MailtoHandlerProvider();
   virtual ~MailtoHandlerProvider();
 
-  // Set up mailto handling for the current browser state.
-  virtual void PrepareMailtoHandling(ios::ChromeBrowserState* browserState);
+  // Sets up mailto handling for |browser_state|.
+  virtual void PrepareMailtoHandling(ios::ChromeBrowserState* browser_state);
+
+  // Unregisters the mailto handler for browser state.
+  virtual void RemoveMailtoHandling();
 
   // Deprecated: Set up mailto handling for the current user.
   // The Signed-In Identity Block should return the primary signed in user.

ios/public/provider/chrome/browser/mailto/mailto_handler_provider.mm

@@ -13,7 +13,9 @@ MailtoHandlerProvider::MailtoHandlerProvider() {}
 MailtoHandlerProvider::~MailtoHandlerProvider() {}
 
 void MailtoHandlerProvider::PrepareMailtoHandling(
-    ios::ChromeBrowserState* browserState) {}
+    ios::ChromeBrowserState* browser_state) {}
+
+void MailtoHandlerProvider::RemoveMailtoHandling() {}
 
 void MailtoHandlerProvider::PrepareMailtoHandling(
     SignedInIdentityBlock signed_in_identity_block,