Fix gradient background invalidation when HTML size changes

third_party/WebKit/Source/core/paint/BoxPaintInvalidator.cpp

Index: third_party/WebKit/Source/core/paint/BoxPaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.cpp
index 9e797d492e1dd2ef7483f973342a2050e26a5fb3..dbcdf4100ccce2776afa6a181f4e0b9d00df214b 100644
--- a/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.cpp
+++ b/third_party/WebKit/Source/core/paint/BoxPaintInvalidator.cpp
@@ -312,13 +312,19 @@ PaintInvalidationReason BoxPaintInvalidator::invalidatePaintIfNeeded() {
 
 bool BoxPaintInvalidator::needsToSavePreviousBoxGeometries() {
   LayoutSize paintInvalidationSize = m_context.newVisualRect.size();
-  // Don't save old box Geometries if the paint rect is empty because we'll
-  // full invalidate once the paint rect becomes non-empty.
-  if (paintInvalidationSize.isEmpty())
-    return false;
 
-  if (m_box.paintedOutputOfObjectHasNoEffectRegardlessOfSize())
-    return false;
+  // The shortcuts doesn't apply to HTML element. ViewPaintInvalidator needs to
+  // know its previous border box size even if it has visibility:hidden (causing
+  // empty paintInvalidationSize) or has no painted output.
+  if (!m_box.node() || !m_box.node()->isHTMLElement()) {
+    // Don't save old box geometries if the paint rect is empty because we'll
+    // fully invalidate once the paint rect becomes non-empty.
+    if (paintInvalidationSize.isEmpty())
+      return false;
+
+    if (m_box.paintedOutputOfObjectHasNoEffectRegardlessOfSize())
+      return false;
+  }
 
   const ComputedStyle& style = m_box.styleRef();
 
@@ -360,15 +366,26 @@ void BoxPaintInvalidator::savePreviousBoxGeometriesIfNeeded() {
   m_box.getMutableForPainting().setHasPreviousBoxGeometries(true);
 }
 
-LayoutSize BoxPaintInvalidator::previousBorderBoxSize() {
-  DCHECK(m_box.hasPreviousBoxGeometries() ==
-         previousBoxGeometriesMap().contains(&m_box));
-  if (m_box.hasPreviousBoxGeometries())
-    return previousBoxGeometriesMap().get(&m_box).borderBoxSize;
+static LayoutSize previousBorderBoxSizeInternal(const LayoutBox& box,
+                                                const LayoutSize& defaultSize) {
+  DCHECK(box.hasPreviousBoxGeometries() ==
+         previousBoxGeometriesMap().contains(&box));
+  if (box.hasPreviousBoxGeometries())
+    return previousBoxGeometriesMap().get(&box).borderBoxSize;
+  return defaultSize;
+}
 
-  // We didn't save the old border box size because it was the same as the size
-  // of oldVisualRect.
-  return m_context.oldVisualRect.size();
+// This is used by ViewPaintInvalidator to get the previous border box size
+// of the HTML element, before the HTML element is paint invalidated.
+LayoutSize BoxPaintInvalidator::previousBorderBoxSize(const LayoutBox& box) {

[chrishtr, 2017/02/16 23:11:25]

It's weird that there are two methods with the same name that use a different
implicit rect. How about just removing these non-static methods and making
everyone pass two args to previousBorderBoxSizeInternal? (which would be
renamed).

[Xianzhu, 2017/02/16 23:39:35]

Done.

+  return previousBorderBoxSizeInternal(box, box.visualRect().size());
+}
+
+// This is used during paint invalidation of the m_box. PaintInvalidator has
+// already updated m_box.visualRect() to the current value, so we need to use
+// context.oldVisualRect as the default value.
+LayoutSize BoxPaintInvalidator::previousBorderBoxSize() {
+  return previousBorderBoxSizeInternal(m_box, m_context.oldVisualRect.size());
 }
 
 LayoutRect BoxPaintInvalidator::previousContentBoxRect() {