Add a nullable string16 class to base. It combines a string16 + a null param

in order to cover all the possible states of a WebKit string.  For strings
where the null state is not meaninfully different from the empty state, this
class should NOT be used.  There are, however, some cases where we do need to
track null.  LocalStorage is an example.  This class should be a fairly light
weight way to do so.  This change also adds implicit conversion to and from
WebStrings.

This also switches LocalStorage's IPCs over to using this new class.

BUG=17343
TEST=none

Review URL: http://codereview.chromium.org/174484

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@24574 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 20 insertions, 24 deletions

diff --git a/chrome/renderer/renderer_webstoragearea_impl.cc b/chrome/renderer/renderer_webstoragearea_impl.cc
index 14f2273..825d967 100644
--- a/chrome/renderer/renderer_webstoragearea_impl.cc
+++ b/chrome/renderer/renderer_webstoragearea_impl.cc
@@ -8,9 +8,11 @@
 #include "chrome/renderer/render_thread.h"
 #include "webkit/api/public/WebString.h"
 
+using WebKit::WebString;
+
 RendererWebStorageAreaImpl::RendererWebStorageAreaImpl(
     int64 namespace_id,
-    const WebKit::WebString& origin)
+    const WebString& origin)
     : namespace_id_(namespace_id),
       origin_(origin),
       storage_area_id_(kUninitializedStorageAreaId),
@@ -45,22 +47,19 @@ unsigned RendererWebStorageAreaImpl::length() {
   return length;
 }
 
-WebKit::WebString RendererWebStorageAreaImpl::key(unsigned index) {
+WebString RendererWebStorageAreaImpl::key(unsigned index) {
   EnsureInitializedAndLocked();
   // Right now this is always sync.  We may want to optimize this by fetching
   // chunks of keys rather than single keys (and flushing the cache on every
   // mutation of the storage area) since this will most often be used to fetch
   // all the keys at once.
-  string16 key;
-  bool key_is_null;
+  NullableString16 key;
   RenderThread::current()->Send(
-      new ViewHostMsg_DOMStorageKey(storage_area_id_, index,
-                                    &key, &key_is_null));
-  return key_is_null ? WebKit::WebString() : WebKit::WebString(key);
+      new ViewHostMsg_DOMStorageKey(storage_area_id_, index, &key));
+  return key;
 }
 
-WebKit::WebString RendererWebStorageAreaImpl::getItem(
-    const WebKit::WebString& webkit_key) {
+WebString RendererWebStorageAreaImpl::getItem(const WebString& webkit_key) {
   EnsureInitializedAndLocked();
   string16 key = webkit_key;
 
@@ -69,23 +68,20 @@ WebKit::WebString RendererWebStorageAreaImpl::getItem(
   if (iterator != cached_items_.end())
     return iterator->second;
   if (cached_invalid_items_.find(key) != cached_invalid_items_.end())
-    return WebKit::WebString();  // Return a "null" string.
+    return WebString();  // Return a "null" string.
 
   // The item is not in the cache, so we must do a sync IPC.  Afterwards,
   // add it to the cache.
-  string16 raw_value;
-  bool value_is_null;
+  NullableString16 raw_value;
   RenderThread::current()->Send(
-      new ViewHostMsg_DOMStorageGetItem(storage_area_id_, key,
-                                        &raw_value, &value_is_null));
-  WebKit::WebString value = value_is_null ? WebKit::WebString()
-                                          : WebKit::WebString(raw_value);
+      new ViewHostMsg_DOMStorageGetItem(storage_area_id_, key, &raw_value));
+  WebString value = raw_value;  // Only do the conversion once.
   SetCache(key, value);
   return value;
 }
 
-void RendererWebStorageAreaImpl::setItem(const WebKit::WebString& key,
-                                         const WebKit::WebString& value,
+void RendererWebStorageAreaImpl::setItem(const WebString& key,
+                                         const WebString& value,
                                          bool& quota_exception) {
   EnsureInitializedAndLocked();
   quota_exception = !UpdateQuota(key, value);
@@ -96,13 +92,13 @@ void RendererWebStorageAreaImpl::setItem(const WebKit::WebString& key,
   SetCache(key, value);
 }
 
-void RendererWebStorageAreaImpl::removeItem(const WebKit::WebString& key) {
+void RendererWebStorageAreaImpl::removeItem(const WebString& key) {
   EnsureInitializedAndLocked();
-  bool update_succeeded = UpdateQuota(key, WebKit::WebString());
+  bool update_succeeded = UpdateQuota(key, WebString());
   DCHECK(update_succeeded);
   RenderThread::current()->Send(
       new ViewHostMsg_DOMStorageRemoveItem(storage_area_id_, key));
-  SetCache(key, WebKit::WebString());
+  SetCache(key, WebString());
 }
 
 void RendererWebStorageAreaImpl::clear() {
@@ -137,8 +133,8 @@ void RendererWebStorageAreaImpl::EnsureInitializedAndLocked() {
   }
 }
 
-bool RendererWebStorageAreaImpl::UpdateQuota(const WebKit::WebString& key,
-                                             const WebKit::WebString& value) {
+bool RendererWebStorageAreaImpl::UpdateQuota(const WebString& key,
+                                             const WebString& value) {
   // TODO(jorlow): Remove once the bytes_left_in_quota values we're getting
   //               are accurate.
   return true;
@@ -160,7 +156,7 @@ bool RendererWebStorageAreaImpl::UpdateQuota(const WebKit::WebString& key,
 }
 
 void RendererWebStorageAreaImpl::SetCache(const string16& key,
-                                          const WebKit::WebString& value) {
+                                          const WebString& value) {
   cached_items_.erase(key);
   cached_invalid_items_.erase(key);