Hook up style invalidation for CSS Paint API.

third_party/WebKit/Source/core/css/CSSPaintValue.h

Index: third_party/WebKit/Source/core/css/CSSPaintValue.h
diff --git a/third_party/WebKit/Source/core/css/CSSPaintValue.h b/third_party/WebKit/Source/core/css/CSSPaintValue.h
index 07eb74ca86e61d44b8078e2d150d61312b932427..a5f4ecbbff54c1e090043f3ac74d8cb236c9b3a1 100644
--- a/third_party/WebKit/Source/core/css/CSSPaintValue.h
+++ b/third_party/WebKit/Source/core/css/CSSPaintValue.h
@@ -35,6 +35,17 @@ public:
 
     bool equals(const CSSPaintValue&) const;
 
+    const Vector<CSSPropertyID>& nativeInvalidationProperties() const
+    {
+        DCHECK(m_generator);

[ikilpatrick, 2016/04/19 22:31:25]

This is potentially bad, the m_generator doesn't exist until paint() is called
(as it needs the Document to look up the paint worklet).

In ComputedStyle this could be protected against by a needsFirstPaint() check,
i.e.

// CSSPaintValue.h
bool needsFirstPaint() { return !m_generator; }

// ComputedStyle.h
bool ComputedStyle::diffNeedsPaintInvalidationObjectForPaint(styleImage)
{
  if (paintValue->needsFirstPaint())
    return true;
}

I.e. a paint function which has never been painted is always invalid.

+        return m_generator->nativeInvalidationProperties();
+    }
+    const Vector<AtomicString>& customInvalidationProperties() const
+    {
+        DCHECK(m_generator);
+        return m_generator->customInvalidationProperties();
+    }
+
     DECLARE_TRACE_AFTER_DISPATCH();
 
 private: