Reland "Correctly initialize and test SnapContainerData in cc."

This reverts commit 0fc70abb.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Revert "Correctly initialize and test SnapContainerData in cc."
> 
> This reverts commit 37061f87.
> 
> Reason for revert:
> The layout tests added by this CL is failing on the CL:
> https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Win10/37804
> 
> Original change's description:
> > Correctly initialize and test SnapContainerData in cc.
> > 
> > This patch initializes the rect_ field in SnapContainerData in copy
> > constructor and move constructor. Fixing a snapping issue in the
> > composited pages.
> > 
> > We also adds external/wpt/css/css-scroll-snap/ to the virtual/threaded
> > test suite so that they are tested with the composited cases.
> > 
> > snap-at-user-scroll-end-manual-automation.js calls
> > mouseClickInTarget() of pointerevent_common_input.js. That method
> > invokes programmatic scrolls. The test was written before programmatic
> > scroll snapping was implemented so it worked at that time. However,
> > with programmatic scroll snapping implemented, it will always snap
> > in mouseClickIntarget() and cannot test whether the user scroll snaps.
> > This patch adds a parameter shouldScrollToTarget to mouseClickInTarget
> > to avoid invoking programmatic scrolls in the test.
> > 
> > This patch also checks nullptr for layout_box in
> > ScrollManager::SnapAtGestureScrollEnd() to fix a crash.
> > 
> > Bug: 862406, 862571
> > Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
> > Change-Id: I6a53818cf74421a4100ad6f908158abf302a5b8e
> > Reviewed-on: https://chromium-review.googlesource.com/1132386
> > Commit-Queue: Sandra Sun <sunyunjia@chromium.org>
> > Reviewed-by: Majid Valipour <majidvp@chromium.org>
> > Reviewed-by: Robert Flack <flackr@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#574781}
> 
> TBR=flackr@chromium.org,majidvp@chromium.org,sunyunjia@chromium.org
> 
> Change-Id: I55c77c05c0381c8ac638bd106d2d18b1b4332745
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 862406, 862571
> Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
> Reviewed-on: https://chromium-review.googlesource.com/1136171
> Reviewed-by: Taiju Tsuiki <tzik@chromium.org>
> Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#574825}

TBR=flackr@chromium.org,majidvp@chromium.org,sunyunjia@chromium.org,tzik@chromium.org

Change-Id: I4a9480b68c15e0dfcfd13df6ed6c0e6b8ab5a8e3
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 862406, 862571
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/1136671Reviewed-by: Sandra Sun <sunyunjia@chromium.org>
Commit-Queue: Sandra Sun <sunyunjia@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574926}

cc/input/scroll_snap_data.cc

@@ -73,24 +73,15 @@ SnapContainerData::SnapContainerData(ScrollSnapType type,
 
 SnapContainerData::SnapContainerData(const SnapContainerData& other) = default;
 
-SnapContainerData::SnapContainerData(SnapContainerData&& other)
-    : scroll_snap_type_(other.scroll_snap_type_),
-      max_position_(other.max_position_),
-      proximity_range_(other.proximity_range_),
-      snap_area_list_(std::move(other.snap_area_list_)) {}
+SnapContainerData::SnapContainerData(SnapContainerData&& other) = default;
 
 SnapContainerData::~SnapContainerData() = default;
 
 SnapContainerData& SnapContainerData::operator=(
     const SnapContainerData& other) = default;
 
-SnapContainerData& SnapContainerData::operator=(SnapContainerData&& other) {
-  scroll_snap_type_ = other.scroll_snap_type_;
-  max_position_ = other.max_position_;
-  proximity_range_ = other.proximity_range_;
-  snap_area_list_ = std::move(other.snap_area_list_);
-  return *this;
-}
+SnapContainerData& SnapContainerData::operator=(SnapContainerData&& other) =
+    default;
 
 void SnapContainerData::AddSnapAreaData(SnapAreaData snap_area_data) {
   snap_area_list_.push_back(snap_area_data);

third_party/WebKit/LayoutTests/VirtualTestSuites

@@ -34,6 +34,11 @@
     "base": "http/tests/worklet",
     "args": ["--enable-threaded-compositing"]
   },
+  {
+    "prefix": "threaded",
+    "base": "external/wpt/css/css-scroll-snap",
+    "args": ["--enable-threaded-compositing"]
+  },
   {
     "prefix": "threaded",
     "base": "compositing/webgl",

third_party/WebKit/LayoutTests/external/wpt/css/css-scroll-snap/snap-at-user-scroll-end-manual.html

@@ -45,6 +45,7 @@ body {
 </div>
 
 <script>
+var snap_test = async_test('Tests that window should snap at user scroll end.');
 var body = document.body;
 var button = document.getElementById("btn");
 var target = document.getElementById("target");
@@ -80,7 +81,7 @@ button.onclick = function() {
   // To make the test result visible.
   var content = document.getElementById("content");
   body.removeChild(content);
-  done();
+  snap_test.done();
 }
 
-</script>
\ No newline at end of file
+</script>

third_party/WebKit/LayoutTests/external/wpt_automation/css/css-scroll-snap/snap-at-user-scroll-end-manual-automation.js

@@ -36,9 +36,10 @@ function waitForAnimationEnd() {
 }
 
 function inject_input() {
-  return smoothScroll(2, 20, 20, 'downright', 4000).then(() => {
+  return smoothScroll(100, 20, 20, 'downright', 4000).then(() => {
     return waitForAnimationEnd();
   }).then(() => {
-    return mouseClickInTarget('#btn');
+    return mouseClickInTarget('#btn', undefined, 'left',
+        /* shouldScrollToTarget = */ false);
   });
-}
\ No newline at end of file
+}

third_party/WebKit/LayoutTests/external/wpt_automation/pointerevents/pointerevent_common_input.js

@@ -107,7 +107,7 @@ function mouseChordedButtonPress(targetSelector) {
   });
 }
 
-function mouseClickInTarget(targetSelector, targetFrame, button) {
+function mouseClickInTarget(targetSelector, targetFrame, button, shouldScrollToTarget = true) {
   var targetDocument = document;
   var frameLeft = 0;
   var frameTop = 0;
@@ -122,7 +122,8 @@ function mouseClickInTarget(targetSelector, targetFrame, button) {
   }
   return new Promise(function(resolve, reject) {
     if (window.chrome && chrome.gpuBenchmarking) {
-      scrollPageIfNeeded(targetSelector, targetDocument);
+      if (shouldScrollToTarget)
+        scrollPageIfNeeded(targetSelector, targetDocument);
       var target = targetDocument.querySelector(targetSelector);
       var targetRect = target.getBoundingClientRect();
       var xPosition = frameLeft + targetRect.left + boundaryOffset;

third_party/WebKit/LayoutTests/virtual/threaded/external/wpt/css/css-scroll-snap/README.txt

+# This suite runs the test in external/wpt/css/css-scroll-snap/ with
+# --enable-threaded-compositing
\ No newline at end of file

third_party/blink/renderer/core/input/scroll_manager.cc

@@ -628,10 +628,10 @@ void ScrollManager::SnapAtGestureScrollEnd() {
     return;
   SnapCoordinator* snap_coordinator =
       frame_->GetDocument()->GetSnapCoordinator();
-  if (!snap_coordinator)
+  LayoutBox* layout_box = LayoutBoxForSnapping();
+  if (!snap_coordinator || !layout_box)
     return;
 
-  LayoutBox* layout_box = LayoutBoxForSnapping();
   snap_coordinator->PerformSnapping(*layout_box,
                                     did_scroll_x_for_scroll_gesture_,
                                     did_scroll_y_for_scroll_gesture_);