Move NotificationObserver, NotificationSource, and NotificationDetails to content/public/browser.

This patch got way bigger than I wanted, but once I moved NotificationDetails, I figured I might as well mvoe the others since they're in the same files. In hindsight, I should have converted a subset of files at a time by leaving a using statement in the header.

BUG=98716
TBR=joi

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@106196 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/browser/host_zoom_map.cc b/content/browser/host_zoom_map.cc
index 6eaba75c..6aa228b 100644
--- a/content/browser/host_zoom_map.cc
+++ b/content/browser/host_zoom_map.cc
@@ -63,8 +63,8 @@
 
   NotificationService::current()->Notify(
       content::NOTIFICATION_ZOOM_LEVEL_CHANGED,
-      Source<HostZoomMap>(this),
-      Details<const std::string>(&host));
+      content::Source<HostZoomMap>(this),
+      content::Details<const std::string>(&host));
 }
 
 double HostZoomMap::GetTemporaryZoomLevel(int render_process_id,
@@ -111,21 +111,23 @@
   std::string host;
   NotificationService::current()->Notify(
       content::NOTIFICATION_ZOOM_LEVEL_CHANGED,
-      Source<HostZoomMap>(this),
-      Details<const std::string>(&host));
+      content::Source<HostZoomMap>(this),
+      content::Details<const std::string>(&host));
 }
 
 void HostZoomMap::Observe(
     int type,
-    const NotificationSource& source,
-    const NotificationDetails& details) {
+    const content::NotificationSource& source,
+    const content::NotificationDetails& details) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   switch (type) {
     case content::NOTIFICATION_RENDER_VIEW_HOST_WILL_CLOSE_RENDER_VIEW: {
       base::AutoLock auto_lock(lock_);
-      int render_view_id = Source<RenderViewHost>(source)->routing_id();
-      int render_process_id = Source<RenderViewHost>(source)->process()->id();
+      int render_view_id =
+          content::Source<RenderViewHost>(source)->routing_id();
+      int render_process_id =
+          content::Source<RenderViewHost>(source)->process()->id();
 
       for (size_t i = 0; i < temporary_zoom_levels_.size(); ++i) {
         if (temporary_zoom_levels_[i].render_process_id == render_process_id &&