Merge "Reduce history item saving frequency when scrolling." into honeycomb

1 files changed, 9 insertions, 1 deletions

diff --git a/WebKit/android/jni/WebViewCore.cpp b/WebKit/android/jni/WebViewCore.cpp
index 149176a..3328acd 100644
--- a/WebKit/android/jni/WebViewCore.cpp
+++ b/WebKit/android/jni/WebViewCore.cpp
@@ -1175,7 +1175,15 @@ void WebViewCore::setScrollOffset(int moveGeneration, int userScrolled, int dx,
         // background, so scroll position will be restored if browser gets
         // killed while in background.
         WebCore::HistoryController* history = m_mainFrame->loader()->history();
-        history->saveScrollPositionAndViewStateToItem(history->currentItem());
+        // Because the history item saving could be heavy for large sites and
+        // scrolling can generate lots of small scroll offset, the following code
+        // reduces the saving frequency.
+        static const int MIN_SCROLL_DIFF = 32;
+        WebCore::IntPoint currentPoint = history->currentItem()->scrollPoint();
+        if (std::abs(currentPoint.x() - dx) >= MIN_SCROLL_DIFF ||
+            std::abs(currentPoint.y() - dy) >= MIN_SCROLL_DIFF) {
+            history->saveScrollPositionAndViewStateToItem(history->currentItem());
+        }
 
         // update the currently visible screen
         sendPluginVisibleScreen();