Take 2: Preload the visited link db on the file thread if

the file exists. Otherwise, just load like normal on the UI thread.

This failed before because the browser may have shutdown before the
posted task ran.  When the posted task finally runs, it tried to
use the profile, but the profile was already deleted.  Make a small
change to VisitedLinkMaster so GetDatabaseFileName no longer depends
on the profile.

BUG=24163

Review URL: http://codereview.chromium.org/507047

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@35991 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 95 insertions, 10 deletions

diff --git a/chrome/browser/profile.cc b/chrome/browser/profile.cc
index 3231ede2..fefbc8d 100644
--- a/chrome/browser/profile.cc
+++ b/chrome/browser/profile.cc
@@ -125,6 +125,87 @@ bool HasACacheSubdir(const FilePath &dir) {
 
 }  // namespace
 
+// This helper class owns the VisitedLinkMaster and exposes a way to load it
+// from on the file thread.
+class VisitedLinkCreator
+    : public base::RefCountedThreadSafe<VisitedLinkCreator> {
+ public:
+  enum LoadState {
+    NOT_LOADED,
+    FILE_LOAD_FAILED,
+    LOAD_FINISHED
+  };
+
+  explicit VisitedLinkCreator(Profile* profile)
+      : listener_(new VisitedLinkEventListener()),
+        profile_(profile),
+        load_state_(NOT_LOADED) {
+    visited_link_master_.reset(new VisitedLinkMaster(listener_.get(),
+                                                     profile_));
+  }
+
+  // Preload the visited link master on the file thread.
+  void Preload() {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
+    ChromeThread::PostTask(ChromeThread::FILE, FROM_HERE, NewRunnableMethod(
+        this, &VisitedLinkCreator::LoadBackground));
+  }
+
+  // This method can return NULL if for some reason we can't initialize the
+  // visited link master.
+  VisitedLinkMaster* GetMaster() {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::UI));
+    // Go ahead and try to load the VisitedLink table.  If the data was
+    // preloaded, Load() does nothing.
+    AutoLock l(lock_);
+    if (LOAD_FINISHED != load_state_) {
+      bool success = false;
+      if (FILE_LOAD_FAILED == load_state_) {
+        success = visited_link_master_->InitFromScratch();
+      } else if (NOT_LOADED == load_state_) {
+        // We haven't tried to load from file yet, so go ahead and do that.
+        success = visited_link_master_->Init();
+      }
+
+      if (!success) {
+        NOTREACHED() << "Failed to init visited link master.";
+        visited_link_master_.reset();
+      }
+      load_state_ = LOAD_FINISHED;
+    }
+
+    // We don't need to lock here because after Load() has been called, we
+    // never change vistied_link_master_.
+    return visited_link_master_.get();
+  }
+
+ private:
+  // Tries to load the visited link database from the UI thread.
+  void LoadBackground() {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::FILE));
+    AutoLock l(lock_);
+    if (NOT_LOADED != load_state_)
+      return;
+
+    // We only want to try to load the data from a file (it's not thread safe
+    // to InitFromScratch on the file thread).
+    load_state_ = visited_link_master_->InitFromFile() ? LOAD_FINISHED
+                                                       : FILE_LOAD_FAILED;
+  }
+
+  scoped_ptr<VisitedLinkMaster::Listener> listener_;
+  Profile* profile_;
+
+  // This lock protects visited_link_master_ and load_state_.
+  Lock lock_;
+  scoped_ptr<VisitedLinkMaster> visited_link_master_;
+  // Once created_ is true, we can stop trying to create and init the
+  // VisitedLinkMaster.
+  LoadState load_state_;
+
+  DISALLOW_COPY_AND_ASSIGN(VisitedLinkCreator);
+};
+
 // A pointer to the request context for the default profile.  See comments on
 // Profile::GetDefaultRequestContext.
 URLRequestContextGetter* Profile::default_request_context_;
@@ -214,7 +295,9 @@ class OffTheRecordProfileImpl : public Profile,
     return reinterpret_cast<ProfileId>(this);
   }
 
-  virtual FilePath GetPath() { return profile_->GetPath(); }
+  virtual FilePath GetPath() {
+    return profile_->GetPath();
+  }
 
   virtual bool IsOffTheRecord() {
     return true;
@@ -245,6 +328,8 @@ class OffTheRecordProfileImpl : public Profile,
     return NULL;
   }
 
+  virtual void PreloadVisitedLinkMaster() {}
+
   virtual ExtensionsService* GetExtensionsService() {
     return NULL;
   }
@@ -567,7 +652,6 @@ class OffTheRecordProfileImpl : public Profile,
 
 ProfileImpl::ProfileImpl(const FilePath& path)
     : path_(path),
-      visited_link_event_listener_(new VisitedLinkEventListener()),
       extension_devtools_manager_(NULL),
       request_context_(NULL),
       media_request_context_(NULL),
@@ -814,15 +898,16 @@ webkit_database::DatabaseTracker* ProfileImpl::GetDatabaseTracker() {
 }
 
 VisitedLinkMaster* ProfileImpl::GetVisitedLinkMaster() {
-  if (!visited_link_master_.get()) {
-    scoped_ptr<VisitedLinkMaster> visited_links(
-      new VisitedLinkMaster(visited_link_event_listener_.get(), this));
-    if (!visited_links->Init())
-      return NULL;
-    visited_link_master_.swap(visited_links);
-  }
+  if (!visited_link_creator_.get())
+    visited_link_creator_ = new VisitedLinkCreator(this);
+  return visited_link_creator_->GetMaster();
+}
 
-  return visited_link_master_.get();
+void ProfileImpl::PreloadVisitedLinkMaster() {
+  if (!visited_link_creator_.get()) {
+    visited_link_creator_ = new VisitedLinkCreator(this);
+    visited_link_creator_->Preload();
+  }
 }
 
 ExtensionsService* ProfileImpl::GetExtensionsService() {