4 files changed, 37 insertions, 14 deletions

diff --git a/shared/native_view_qt.cpp b/shared/native_view_qt.cpp
index d95cb6957..1a5716549 100644
--- a/shared/native_view_qt.cpp
+++ b/shared/native_view_qt.cpp
@@ -44,9 +44,9 @@ QWindow* QWidgetNativeView::window() const
     return QWidget::windowHandle();
 }
 
-void QWidgetNativeView::update()
+void QWidgetNativeView::update(const QRect& rect)
 {
-    QWidget::update();
+    QWidget::update(rect);
 }
 
 void QWidgetNativeView::setBackingStore(BackingStoreQt* backingStore)
@@ -120,9 +120,9 @@ QWindow* QQuickNativeView::window() const
     return QQuickPaintedItem::window();
 }
 
-void QQuickNativeView::update()
+void QQuickNativeView::update(const QRect& rect)
 {
-    QQuickPaintedItem::update();
+    QQuickPaintedItem::update(rect);
 }
 
 void QQuickNativeView::paint(QPainter *painter)
diff --git a/shared/native_view_qt.h b/shared/native_view_qt.h
index 80bb24e87..6a15701e8 100644
--- a/shared/native_view_qt.h
+++ b/shared/native_view_qt.h
@@ -26,7 +26,7 @@ public:
     virtual void hide() = 0;
     virtual bool isVisible() const = 0;
     virtual QWindow* window() const = 0;
-    virtual void update() = 0;
+    virtual void update(const QRect& rect = QRect()) = 0;
 };
 
 class QWidgetNativeView : public QWidget, public NativeViewQt
@@ -40,7 +40,7 @@ public:
     virtual void hide();
     virtual bool isVisible() const;
     virtual QWindow* window() const;
-    virtual void update();
+    virtual void update(const QRect& rect = QRect());
 
     QPainter* painter();
 
@@ -67,7 +67,7 @@ public:
     virtual void hide();
     virtual bool isVisible() const;
     virtual QWindow* window() const;
-    virtual void update();
+    virtual void update(const QRect& rect = QRect());
 
     void paint(QPainter *painter);
     void resize(int width, int height);
diff --git a/shared/render_widget_host_view_qt.cpp b/shared/render_widget_host_view_qt.cpp
index 351030c7a..4fcdcbf00 100644
--- a/shared/render_widget_host_view_qt.cpp
+++ b/shared/render_widget_host_view_qt.cpp
@@ -91,6 +91,7 @@ void RenderWidgetHostViewPort::GetDefaultScreenInfo(WebKit::WebScreenInfo* resul
 RenderWidgetHostViewQt::RenderWidgetHostViewQt(content::RenderWidgetHost* widget)
     : m_host(content::RenderWidgetHostImpl::From(widget))
     , m_view(0)
+    , about_to_validate_and_paint_(false)
 {
     m_host->SetView(this);
 }
@@ -346,14 +347,20 @@ void RenderWidgetHostViewQt::DidUpdateBackingStore(const gfx::Rect& scroll_rect,
     if (!m_view || !m_view->isVisible())
         return;
 
-    Paint(scroll_rect);
+    if (about_to_validate_and_paint_)
+        invalid_rect_.Union(scroll_rect);
+    else
+        Paint(scroll_rect);
 
     for (size_t i = 0; i < copy_rects.size(); ++i) {
         gfx::Rect rect = gfx::SubtractRects(copy_rects[i], scroll_rect);
         if (rect.IsEmpty())
             continue;
 
-        Paint(rect);
+        if (about_to_validate_and_paint_)
+            invalid_rect_.Union(rect);
+        else
+            Paint(rect);
     }
 }
 
@@ -469,15 +476,23 @@ void RenderWidgetHostViewQt::OnAccessibilityNotifications(const std::vector<Acce
     QT_NOT_YET_IMPLEMENTED
 }
 
-void RenderWidgetHostViewQt::Paint(const gfx::Rect& scroll_rect)
+void RenderWidgetHostViewQt::Paint(const gfx::Rect& damage_rect)
 {
+    DCHECK(!about_to_validate_and_paint_);
+
+    invalid_rect_ = damage_rect;
+    about_to_validate_and_paint_ = true;
+
     bool force_create = !m_host->empty();
     BackingStoreQt* backing_store = static_cast<BackingStoreQt*>(m_host->GetBackingStore(force_create));
+
+    // Calling GetBackingStore maybe have changed |invalid_rect_|...
+    about_to_validate_and_paint_ = false;
+
     if (backing_store && m_view) {
-        QRectF r  = m_view->screenRect();
-        QRect rect(0, 0, r.width(), r.height());
         m_view->setBackingStore(backing_store);
-        m_view->update();
+        QRect r(invalid_rect_.x(), invalid_rect_.y(), invalid_rect_.width(), invalid_rect_.height());
+        m_view->update(r);
     }
 }
 
diff --git a/shared/render_widget_host_view_qt.h b/shared/render_widget_host_view_qt.h
index 94faf8205..d21cbf051 100644
--- a/shared/render_widget_host_view_qt.h
+++ b/shared/render_widget_host_view_qt.h
@@ -128,13 +128,21 @@ public:
     void handleWheelEvent(QWheelEvent*);
     void handleFocusEvent(QFocusEvent*);
 private:
-    void Paint(const gfx::Rect& scroll_rect);
+    void Paint(const gfx::Rect& damage_rect);
 
     bool IsPopup() const;
 
     content::RenderWidgetHostImpl *m_host;
     NativeViewQt *m_view;
     gfx::Size m_requestedSize;
+
+    // This is true when we are currently painting and thus should handle extra
+    // paint requests by expanding the invalid rect rather than actually
+    // painting.
+    bool about_to_validate_and_paint_;
+
+    // This is the rectangle which we'll paint.
+    gfx::Rect invalid_rect_;
 };
 
 }