Add ability to exclude page state in ContentSerializedNavigationBuilder

Serialization of page state can be a cpu intensive process as the serializer
must recursively traverse a tree of iframes. One of the common cases for
serializing navigation entries is Sync, which does not actually use the
encoded page state information.

This CL adds a new SerializationOptions param and support for using it to
exclude the page state when serializing a NavigationEntry, allowing Sync's
tab delegate to bypass encoding the page state.

Bug: 738187
Change-Id: Ib758db83e3f688c7016044e16a9f2818062e1da0
Reviewed-on: https://chromium-review.googlesource.com/560696
Commit-Queue: Nicolas Zea <zea@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486125}

chrome/browser/ui/sync/tab_contents_synced_tab_delegate.cc

@@ -114,9 +114,13 @@ void TabContentsSyncedTabDelegate::GetSerializedNavigationAtIndex(
     sessions::SerializedNavigationEntry* serialized_entry) const {
   NavigationEntry* entry = GetPossiblyPendingEntryAtIndex(web_contents_, i);
   if (entry) {
+    // Explicitly exclude page state when serializing the navigation entry.
+    // Sync ignores the page state anyway (e.g. form data is not synced), and
+    // the page state can be expensive to serialize.
     *serialized_entry =
         sessions::ContentSerializedNavigationBuilder::FromNavigationEntry(
-            i, *entry);
+            i, *entry,
+            sessions::ContentSerializedNavigationBuilder::EXCLUDE_PAGE_STATE);
   }
 }
 

components/sessions/content/content_serialized_navigation_builder.cc

@@ -22,7 +22,8 @@ namespace sessions {
 SerializedNavigationEntry
 ContentSerializedNavigationBuilder::FromNavigationEntry(
     int index,
-    const content::NavigationEntry& entry) {
+    const content::NavigationEntry& entry,
+    SerializationOptions serialization_options) {
   SerializedNavigationEntry navigation;
   navigation.index_ = index;
   navigation.unique_id_ = entry.GetUniqueID();
@@ -30,7 +31,8 @@ ContentSerializedNavigationBuilder::FromNavigationEntry(
   navigation.referrer_policy_ = entry.GetReferrer().policy;
   navigation.virtual_url_ = entry.GetVirtualURL();
   navigation.title_ = entry.GetTitle();
-  navigation.encoded_page_state_ = entry.GetPageState().ToEncodedData();
+  if (!(serialization_options & SerializationOptions::EXCLUDE_PAGE_STATE))
+    navigation.encoded_page_state_ = entry.GetPageState().ToEncodedData();
   navigation.transition_type_ = entry.GetTransitionType();
   navigation.has_post_data_ = entry.GetHasPostData();
   navigation.post_id_ = entry.GetPostID();

components/sessions/content/content_serialized_navigation_builder.h

@@ -22,11 +22,25 @@ class SerializedNavigationEntry;
 // classes.
 class SESSIONS_EXPORT ContentSerializedNavigationBuilder {
  public:
+  // Set of options for serializing a navigation. Multiple options can be
+  // combined by bit masking.
+  enum SerializationOptions {
+    // Serialized all available navigation data.
+    DEFAULT = 0x0,
+
+    // Exclude page state data. Serializing page state data can involve heavy
+    // processing on pages with deep iframe trees, so should be avoided if not
+    // necessary.
+    EXCLUDE_PAGE_STATE = 0x1,
+  };
+
   // Construct a SerializedNavigationEntry for a particular index from the given
   // NavigationEntry.
   static SerializedNavigationEntry FromNavigationEntry(
       int index,
-      const content::NavigationEntry& entry);
+      const content::NavigationEntry& entry,
+      SerializationOptions serialization_options =
+          SerializationOptions::DEFAULT);
 
   // Convert the given SerializedNavigationEntry into a NavigationEntry with the
   // given context.  The NavigationEntry will have a transition type of

components/sessions/content/content_serialized_navigation_builder_unittest.cc

@@ -161,6 +161,26 @@ TEST_F(ContentSerializedNavigationBuilderTest, FromNavigationEntry) {
             navigation.extended_info_map().at(kExtendedInfoKey2));
 }
 
+// Test effect of the navigation serialization options.
+TEST_F(ContentSerializedNavigationBuilderTest,
+       FromNavigationEntrySerializationOptions) {
+  const std::unique_ptr<content::NavigationEntry> navigation_entry(
+      MakeNavigationEntryForTest());
+
+  const SerializedNavigationEntry& default_navigation =
+      ContentSerializedNavigationBuilder::FromNavigationEntry(
+          test_data::kIndex, *navigation_entry,
+          ContentSerializedNavigationBuilder::DEFAULT);
+  EXPECT_EQ(test_data::kEncodedPageState,
+            default_navigation.encoded_page_state());
+
+  const SerializedNavigationEntry& excluded_page_state_navigation =
+      ContentSerializedNavigationBuilder::FromNavigationEntry(
+          test_data::kIndex, *navigation_entry,
+          ContentSerializedNavigationBuilder::EXCLUDE_PAGE_STATE);
+  EXPECT_TRUE(excluded_page_state_navigation.encoded_page_state().empty());
+}
+
 // Create a NavigationEntry, then create another one by converting to
 // a SerializedNavigationEntry and back.  The new one should match the old one
 // except for fields that aren't preserved, which should be set to