GSB uses delta_hints to calculate scrolling chain.

third_party/WebKit/Source/web/tests/WebFrameTest.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 10098 matching lines @@
     WebGestureEvent event(type, WebInputEvent::kNoModifiers,
                           WebInputEvent::kTimeStampForTesting);
     // TODO(wjmaclean): Make sure that touchpad device is only ever used for
     // gesture scrolling event types.
     event.source_device = GetParam();
     event.x = 100;
     event.y = 100;
     if (type == WebInputEvent::kGestureScrollUpdate) {
       event.data.scroll_update.delta_x = delta_x;
       event.data.scroll_update.delta_y = delta_y;
+    } else if (type == WebInputEvent::kGestureScrollBegin) {
+      event.data.scroll_begin.delta_x_hint = delta_x;
+      event.data.scroll_begin.delta_y_hint = delta_y;
     }
     return WebCoalescedInputEvent(event);
   }
 
-  void ScrollBegin(FrameTestHelpers::WebViewHelper* web_view_helper) {
-    web_view_helper->WebView()->HandleInputEvent(
-        GenerateEvent(WebInputEvent::kGestureScrollBegin));
+  void ScrollBegin(FrameTestHelpers::WebViewHelper* web_view_helper,
+                   float delta_x_hint,
+                   float delta_y_hint) {
+    web_view_helper->WebView()->HandleInputEvent(GenerateEvent(
+        WebInputEvent::kGestureScrollBegin, delta_x_hint, delta_y_hint));
   }
 
   void ScrollUpdate(FrameTestHelpers::WebViewHelper* web_view_helper,
                     float delta_x,
                     float delta_y) {
     web_view_helper->WebView()->HandleInputEvent(
         GenerateEvent(WebInputEvent::kGestureScrollUpdate, delta_x, delta_y));
   }
 
   void ScrollEnd(FrameTestHelpers::WebViewHelper* web_view_helper) {
@@ skipping 12 matching lines @@
   OverscrollWebViewClient client;
   RegisterMockedHttpURLLoad("overscroll/overscroll.html");
   FrameTestHelpers::WebViewHelper web_view_helper;
   web_view_helper.InitializeAndLoad(base_url_ + "overscroll/overscroll.html",
                                     true, nullptr, &client, nullptr,
                                     ConfigureAndroid);
   web_view_helper.Resize(WebSize(200, 200));
 
   // Calculation of accumulatedRootOverscroll and unusedDelta on multiple
   // scrollUpdate.
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, -300, -316);
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(8, 16), WebFloatSize(8, 16),
                                     WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, -308, -316);
   Mock::VerifyAndClearExpectations(&client);
 
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(0, 13), WebFloatSize(8, 29),
                                     WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, -13);
   Mock::VerifyAndClearExpectations(&client);
 
@@ skipping 27 matching lines @@
 TEST_P(WebFrameOverscrollTest,
        AccumulatedOverscrollAndUnusedDeltaValuesOnDifferentAxesOverscroll) {
   OverscrollWebViewClient client;
   RegisterMockedHttpURLLoad("overscroll/div-overscroll.html");
   FrameTestHelpers::WebViewHelper web_view_helper;
   web_view_helper.InitializeAndLoad(
       base_url_ + "overscroll/div-overscroll.html", true, nullptr, &client,
       nullptr, ConfigureAndroid);
   web_view_helper.Resize(WebSize(200, 200));
 
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, -316);
 
   // Scroll the Div to the end.
   EXPECT_CALL(client, DidOverscroll(_, _, _, _)).Times(0);
   ScrollUpdate(&web_view_helper, 0, -316);
   Mock::VerifyAndClearExpectations(&client);
 
   ScrollEnd(&web_view_helper);
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, -100);
 
   // Now On Scrolling DIV, scroll is bubbled and root layer is over-scrolled.
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(0, 100), WebFloatSize(0, 100),
                                     WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, -100);
   ScrollUpdate(&web_view_helper, 0, -100);
   Mock::VerifyAndClearExpectations(&client);
 
   // TODO(bokan): This has never worked but by the accident that this test was
   // being run in a WebView without a size. This test should be fixed along with
@@ skipping 18 matching lines @@
 
 TEST_P(WebFrameOverscrollTest, RootLayerOverscrolledOnInnerDivOverScroll) {
   OverscrollWebViewClient client;
   RegisterMockedHttpURLLoad("overscroll/div-overscroll.html");
   FrameTestHelpers::WebViewHelper web_view_helper;
   web_view_helper.InitializeAndLoad(
       base_url_ + "overscroll/div-overscroll.html", true, nullptr, &client,
       nullptr, ConfigureAndroid);
   web_view_helper.Resize(WebSize(200, 200));
 
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, -316);
 
   // Scroll the Div to the end.
   EXPECT_CALL(client, DidOverscroll(_, _, _, _)).Times(0);
   ScrollUpdate(&web_view_helper, 0, -316);
   Mock::VerifyAndClearExpectations(&client);
 
   ScrollEnd(&web_view_helper);
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, -150);
 
   // Now On Scrolling DIV, scroll is bubbled and root layer is over-scrolled.
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(0, 50), WebFloatSize(0, 50),
                                     WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, -150);
   Mock::VerifyAndClearExpectations(&client);
 }
 
 TEST_P(WebFrameOverscrollTest, RootLayerOverscrolledOnInnerIFrameOverScroll) {
   OverscrollWebViewClient client;
   RegisterMockedHttpURLLoad("overscroll/iframe-overscroll.html");
   RegisterMockedHttpURLLoad("overscroll/scrollable-iframe.html");
   FrameTestHelpers::WebViewHelper web_view_helper;
   web_view_helper.InitializeAndLoad(
       base_url_ + "overscroll/iframe-overscroll.html", true, nullptr, &client,
       nullptr, ConfigureAndroid);
   web_view_helper.Resize(WebSize(200, 200));
 
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, -320);
   // Scroll the IFrame to the end.
   EXPECT_CALL(client, DidOverscroll(_, _, _, _)).Times(0);
 
   // This scroll will fully scroll the iframe but will be consumed before being
   // counted as overscroll.
   ScrollUpdate(&web_view_helper, 0, -320);
 
   // This scroll will again target the iframe but wont bubble further up. Make
   // sure that the unused scroll isn't handled as overscroll.
   ScrollUpdate(&web_view_helper, 0, -50);
   Mock::VerifyAndClearExpectations(&client);
 
   ScrollEnd(&web_view_helper);
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, -150);
 
   // Now On Scrolling IFrame, scroll is bubbled and root layer is over-scrolled.
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(0, 50), WebFloatSize(0, 50),
                                     WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, -150);
   Mock::VerifyAndClearExpectations(&client);
 
   ScrollEnd(&web_view_helper);
 }
 
 TEST_P(WebFrameOverscrollTest, ScaledPageRootLayerOverscrolled) {
   OverscrollWebViewClient client;
   RegisterMockedHttpURLLoad("overscroll/overscroll.html");
   FrameTestHelpers::WebViewHelper web_view_helper;
   WebViewBase* web_view_impl = web_view_helper.InitializeAndLoad(
       base_url_ + "overscroll/overscroll.html", true, nullptr, &client, nullptr,
       ConfigureAndroid);
   web_view_helper.Resize(WebSize(200, 200));
   web_view_impl->SetPageScaleFactor(3.0);
 
   // Calculation of accumulatedRootOverscroll and unusedDelta on scaled page.
   // The point is (99, 99) because we clamp in the division by 3 to 33 so when
   // we go back to viewport coordinates it becomes (99, 99).
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 0, 30);
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(0, -30), WebFloatSize(0, -30),
                                     WebFloatPoint(99, 99), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, 30);
   Mock::VerifyAndClearExpectations(&client);
 
   EXPECT_CALL(client, DidOverscroll(WebFloatSize(0, -30), WebFloatSize(0, -60),
                                     WebFloatPoint(99, 99), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, 30);
   Mock::VerifyAndClearExpectations(&client);
 
@@ skipping 17 matching lines @@
 
 TEST_P(WebFrameOverscrollTest, NoOverscrollForSmallvalues) {
   OverscrollWebViewClient client;
   RegisterMockedHttpURLLoad("overscroll/overscroll.html");
   FrameTestHelpers::WebViewHelper web_view_helper;
   web_view_helper.InitializeAndLoad(base_url_ + "overscroll/overscroll.html",
                                     true, nullptr, &client, nullptr,
                                     ConfigureAndroid);
   web_view_helper.Resize(WebSize(200, 200));
 
-  ScrollBegin(&web_view_helper);
+  ScrollBegin(&web_view_helper, 10, 10);
   EXPECT_CALL(client,
               DidOverscroll(WebFloatSize(-10, -10), WebFloatSize(-10, -10),
                             WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 10, 10);
   Mock::VerifyAndClearExpectations(&client);
 
   EXPECT_CALL(client,
               DidOverscroll(WebFloatSize(0, -0.10), WebFloatSize(-10, -10.10),
                             WebFloatPoint(100, 100), WebFloatSize()));
   ScrollUpdate(&web_view_helper, 0, 0.10);
@@ skipping 1891 matching lines @@
     if (obj->IsText()) {
       LayoutText* layout_text = ToLayoutText(obj);
       text = layout_text->GetText();
       break;
     }
   }
   EXPECT_EQ("foo alt", text.Utf8());
 }
 
 }  // namespace blink