Make removing a transform not crash.

This broke with https://codereview.chromium.org/965013003.
Before that patch, updateTransform was only called on the
RenderLayer itself. Now it's called on the RenderBox,
so we need to null check the RenderLayer.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/969893002

engine/core/rendering/RenderBox.cpp

@@ -184,14 +184,15 @@ void RenderBox::updateTransform(const RenderStyle* oldStyle)
             m_transform.clear();
 
         // Layers with transforms act as clip rects roots, so clear the cached clip rects here.
-        layer()->clipper().clearClipRectsIncludingDescendants();
-    } else if (localHasTransform) {
+        if (layer())
+            layer()->clipper().clearClipRectsIncludingDescendants();
+    } else if (localHasTransform && layer()) {
         layer()->clipper().clearClipRectsIncludingDescendants(AbsoluteClipRects);
     }
 
     updateTransformationMatrix();
 
-    if (had3DTransform != has3DTransform())
+    if (layer() && had3DTransform != has3DTransform())
         layer()->dirty3DTransformedDescendantStatus();
 }
 

tests/styles/transforms-expected.txt

@@ -2,7 +2,8 @@ CONSOLE: unittest-suite-wait-for-done
 CONSOLE: PASS: pixel translate should roundtrip
 CONSOLE: PASS: percent translate should roundtrip
 CONSOLE: PASS: scale should roundtrip
+CONSOLE: PASS: removing a transform should not crash
 CONSOLE: 
-CONSOLE: All 3 tests passed.
+CONSOLE: All 4 tests passed.
 CONSOLE: unittest-suite-success
 DONE

tests/styles/transforms.sky

@@ -48,5 +48,12 @@
     test('scale should roundtrip', () {
       testTransformRoundTrip('scale(1.2, 0.8)', 'matrix(1.2, 0, 0, 0.8, 0, 0)');
     });
+
+    test('removing a transform should not crash', () {
+      testBox.style['transform'] = 'translate(0, 0, 0)';
+      testBox.getBoundingClientRect();
+      testBox.style.removeProperty('transform');
+      testBox.getBoundingClientRect();
+    });
   }
 </script>