Get rid of HitTestChildBlockBackground walk.

I'm not 100% what this was for, but looking at Blink,
it appears that HitTestChildBlockBackground being different
from HitTestBlockBackground had something to do with
multi-column/regions, which we don't have. I believe
this patch doesn't change any behavior.

Also added to the elementFromPoint test in order to
get more test coverage of the hitTesting code.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/924263002

engine/core/rendering/RenderBlock.cpp

@@ -1079,7 +1079,7 @@ bool RenderBlock::nodeAtPoint(const HitTestRequest& request, HitTestResult& resu
     }
 
     // Now hit test our background
-    if (hitTestAction == HitTestBlockBackground || hitTestAction == HitTestChildBlockBackground) {
+    if (hitTestAction == HitTestBlockBackground) {
         LayoutRect boundsRect(adjustedLocation, size());
         if (visibleToHitTestRequest(request) && locationInContainer.intersects(boundsRect)) {
             updateHitTestResult(result, locationInContainer.point() - localOffset);
@@ -1093,12 +1093,8 @@ bool RenderBlock::nodeAtPoint(const HitTestRequest& request, HitTestResult& resu
 
 bool RenderBlock::hitTestContents(const HitTestRequest& request, HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
 {
-    // Hit test our children.
-    HitTestAction childHitTest = hitTestAction;
-    if (hitTestAction == HitTestChildBlockBackgrounds)
-        childHitTest = HitTestChildBlockBackground;
     for (RenderBox* child = lastChildBox(); child; child = child->previousSiblingBox()) {
-        if (!child->hasSelfPaintingLayer() && child->nodeAtPoint(request, result, locationInContainer, accumulatedOffset, childHitTest))
+        if (!child->hasSelfPaintingLayer() && child->nodeAtPoint(request, result, locationInContainer, accumulatedOffset, hitTestAction))
             return true;
     }
 

engine/core/rendering/RenderLayer.cpp

@@ -996,6 +996,7 @@ RenderLayer* RenderLayer::hitTestLayer(RenderLayer* rootLayer, RenderLayer* cont
     }
 
     // Now check our overflow objects.
+    // TODO(ojan): This call has no test coverage.
     hitLayer = hitTestChildren(NormalFlowChildren, rootLayer, request, result, hitTestRect, hitTestLocation,
                            localTransformState.get(), zOffsetForDescendantsPtr, zOffset, unflattenedTransformState.get(), depthSortDescendants);
     if (hitLayer) {

engine/core/rendering/RenderObject.cpp

@@ -1680,10 +1680,6 @@ bool RenderObject::hitTest(const HitTestRequest& request, HitTestResult& result,
     if (hitTestFilter != HitTestSelf) {
         // First test the foreground layer (lines and inlines).
         inside = nodeAtPoint(request, result, locationInContainer, accumulatedOffset, HitTestForeground);
-
-        // Finally test to see if the mouse is in the background (within a child block's background).
-        if (!inside)
-            inside = nodeAtPoint(request, result, locationInContainer, accumulatedOffset, HitTestChildBlockBackgrounds);
     }
 
     // See if the mouse is inside us but not any of our descendants

engine/core/rendering/RenderObject.h

@@ -76,8 +76,6 @@ enum HitTestFilter {
 
 enum HitTestAction {
     HitTestBlockBackground,
-    HitTestChildBlockBackground,
-    HitTestChildBlockBackgrounds,
     HitTestForeground
 };
 

tests/layout/document-elementFromPoint-expected.txt

 CONSOLE: unittest-suite-wait-for-done
 CONSOLE: PASS: should hit test
+CONSOLE: PASS: should hit test child and parent
+CONSOLE: PASS: should hit test child with layered parent
 CONSOLE: 
-CONSOLE: All 1 tests passed.
+CONSOLE: All 3 tests passed.
 CONSOLE: unittest-suite-success
 DONE

tests/layout/document-elementFromPoint.sky

 <sky>
 <style>
-foo { width: 100px; height: 100px; background: blue; }
+foo, parent { width: 100px; height: 100px; background: blue; }
 bar { width: 100px; height: 100px; background: purple; }
+parent { display: paragraph; }
+child { background: salmon; }
 </style>
 <foo /><bar />
+<parent>
+  <child>Foo bar</child>
+</parent>
 <script>
 import "../resources/third_party/unittest/unittest.dart";
 import "../resources/unit.dart";
@@ -24,7 +29,24 @@ void main() {
     // z-order (missing, zero, positive and negative)
     expect(document.elementFromPoint(50, 50).tagName, equals('foo'));
     expect(document.elementFromPoint(50, 150).tagName, equals('bar'));
-    expect(document.elementFromPoint(50, 250).tagName, equals('sky'));
+    expect(document.elementFromPoint(150, 50).tagName, equals('sky'));
+  });
+
+  void hitTestWithChildren() {
+    expect(document.elementFromPoint(50, 210).tagName, equals('child'));
+    // Right of the <child> inline.
+    expect(document.elementFromPoint(95, 210).tagName, equals('parent'));
+    // Below the <child> inline.
+    expect(document.elementFromPoint(50, 275).tagName, equals('parent'));
+  }
+
+  test("should hit test child and parent", () {
+    hitTestWithChildren();
+  });
+
+  test("should hit test child with layered parent", () {
+    document.querySelector('parent').style.setProperty("transform", "translate3d(0, 0, 0)");
+    hitTestWithChildren();
   });
 }
 </script>