[SPv2] Track paint offset change

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

Index: third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
index f9630d3fc0d8b758ddf05e3f662804a7238f168b..de09075bf226e034ba1b6361e1cb5016bd325742 100644
--- a/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
+++ b/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
@@ -529,19 +529,27 @@ ObjectPaintInvalidatorWithContext::invalidatePaintIfNeededWithComputedReason(
 
   switch (reason) {
     case PaintInvalidationNone:
-      // TODO(trchen): Currently we don't keep track of paint offset of layout
-      // objects.  There are corner cases that the display items need to be
-      // invalidated for paint offset mutation, but incurs no pixel difference
-      // (i.e. bounds stay the same) so no rect-based invalidation is issued.
-      // See crbug.com/508383 and crbug.com/515977.  This is a workaround to
-      // force display items to update paint offset. Exclude non-root SVG whose
-      // paint offset is always zero.
-      if ((!m_object.isSVG() || m_object.isSVGRoot()) &&
-          (m_context.forcedSubtreeInvalidationFlags &
-           PaintInvalidatorContext::ForcedSubtreeInvalidationChecking)) {
-        reason = PaintInvalidationLocationChange;
-        break;
+      // There are corner cases that the display items need to be invalidated
+      // for paint offset mutation, but incurs no pixel difference (i.e. bounds
+      // stay the same) so no rect-based invalidation is issued. See
+      // crbug.com/508383 and crbug.com/515977.
+      if (m_context.forcedSubtreeInvalidationFlags &
+          PaintInvalidatorContext::ForcedSubtreeInvalidationChecking) {
+        if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+          if (m_context.oldPaintOffset != m_context.newPaintOffset) {
+            reason = PaintInvalidationLocationChange;
+            break;
+          }
+        } else {
+          // For SPv1, we conservatively assume the object changed paint offset
+          // except for non-root SVG whose paint offset is always zero.

[chrishtr, 2016/11/10 18:42:00]

SPv2 fixes the issue of paint offset always being 0?

[Xianzhu, 2016/11/10 22:51:50]

The paint offsets are always 0 intentionally. For SPv2, they always don't change
because they are always zero. The condition is just to make SPv1 and SPv2
behaves in the same for SVG objects to reduce layout test result differences.
The condition was added before this CL.

+          if (!m_object.isSVG() || m_object.isSVGRoot()) {
+            reason = PaintInvalidationLocationChange;
+            break;
+          }
+        }
       }
+
       if (m_object.isSVG() &&
           (m_context.forcedSubtreeInvalidationFlags &
            PaintInvalidatorContext::ForcedSubtreeSVGResourceChange)) {