Added CHECKs for null pointers in ChromeAppSorting.

These are designed to give us more information about production-only
crashes occurring in ChromeAppSorting. These checks should help narrow
down the times at which extension_scoped_prefs_ is null.

Added TODOs to remove most of the checks later (although I plan to leave
one in as a safeguard).

BUG=476648

Review URL: https://codereview.chromium.org/1055453007

Cr-Commit-Position: refs/heads/master@{#326746}

chrome/browser/extensions/chrome_app_sorting.cc

@@ -60,6 +60,10 @@ void ChromeAppSorting::SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) {
   extension_scoped_prefs_ = prefs;
 }
 
+void ChromeAppSorting::CheckExtensionScopedPrefs() const {
+  CHECK(extension_scoped_prefs_);
+}
+
 void ChromeAppSorting::SetExtensionSyncService(
     ExtensionSyncService* extension_sync_service) {
   extension_sync_service_ = extension_sync_service;
@@ -67,6 +71,7 @@ void ChromeAppSorting::SetExtensionSyncService(
 
 void ChromeAppSorting::Initialize(
     const extensions::ExtensionIdList& extension_ids) {
+  CHECK(extension_scoped_prefs_);
   InitializePageOrdinalMap(extension_ids);
 
   MigrateAppIndex(extension_ids);
@@ -470,6 +475,9 @@ syncer::StringOrdinal ChromeAppSorting::GetMinOrMaxAppLaunchOrdinalsOnPage(
 
 void ChromeAppSorting::InitializePageOrdinalMap(
     const extensions::ExtensionIdList& extension_ids) {
+  // TODO(mgiuca): Added this CHECK to try and diagnose http://crbug.com/476648.
+  // Remove it after the investigation is concluded.
+  CHECK(extension_scoped_prefs_);
   for (extensions::ExtensionIdList::const_iterator ext_it =
            extension_ids.begin(); ext_it != extension_ids.end(); ++ext_it) {
     AddOrdinalMapping(*ext_it,

chrome/browser/extensions/chrome_app_sorting.h

@@ -29,6 +29,7 @@ class ChromeAppSorting : public AppSorting {
 
   // AppSorting implementation:
   void SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) override;
+  void CheckExtensionScopedPrefs() const override;
   void SetExtensionSyncService(
       ExtensionSyncService* extension_sync_service) override;
   void Initialize(const extensions::ExtensionIdList& extension_ids) override;

extensions/browser/app_sorting.h

@@ -27,11 +27,17 @@ class AppSorting {
   // caller.
   virtual void SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) = 0;
 
+  // CHECKs that SetExtensionScopedPrefs has been called with a non-null object.
+  // TODO(mgiuca): Added this to try and diagnose http://crbug.com/476648.
+  // Remove it after the investigation is concluded.
+  virtual void CheckExtensionScopedPrefs() const = 0;
+
   // Sets up the ExtensionSyncService to inform of changes that require syncing.
   virtual void SetExtensionSyncService(
       ExtensionSyncService* extension_sync_service) = 0;
 
   // Properly initializes internal values that require |extension_ids|.
+  // SetExtensionScopedPrefs must have been called prior to this.
   virtual void Initialize(const extensions::ExtensionIdList& extension_ids) = 0;
 
   // Resolves any conflicts the might be created as a result of syncing that

extensions/browser/extension_prefs.cc

@@ -1866,7 +1866,11 @@ ExtensionPrefs::ExtensionPrefs(
       app_sorting_(app_sorting.Pass()),
       time_provider_(time_provider.Pass()),
       extensions_disabled_(extensions_disabled) {
+  // TODO(mgiuca): Added these checks to try and diagnose
+  // http://crbug.com/476648. Remove them after the investigation is concluded.
+  CHECK(this);
   app_sorting_->SetExtensionScopedPrefs(this);
+  app_sorting_->CheckExtensionScopedPrefs();
   MakePathsRelative();
 
   // Ensure that any early observers are watching before prefs are initialized.

extensions/browser/null_app_sorting.cc

@@ -26,6 +26,9 @@ NullAppSorting::~NullAppSorting() {
 void NullAppSorting::SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) {
 }
 
+void NullAppSorting::CheckExtensionScopedPrefs() const {
+}
+
 void NullAppSorting::SetExtensionSyncService(
     ExtensionSyncService* extension_sync_service) {
 }

extensions/browser/null_app_sorting.h

@@ -19,6 +19,7 @@ class NullAppSorting : public AppSorting {
 
   // AppSorting overrides:
   void SetExtensionScopedPrefs(ExtensionScopedPrefs* prefs) override;
+  void CheckExtensionScopedPrefs() const override;
   void SetExtensionSyncService(
       ExtensionSyncService* extension_sync_service) override;
   void Initialize(const ExtensionIdList& extension_ids) override;