Use a new Supplement constructor for Supplement<Document> (Part 1)

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

Index: third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
diff --git a/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp b/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
index e34e0238841ae7e06a7734388aff45a501b3b495..7dfca3c6335b48203948ee1c8b6e493d518768da 100644
--- a/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
+++ b/third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetector.cpp
@@ -36,7 +36,7 @@ FirstMeaningfulPaintDetector::FirstMeaningfulPaintDetector(
           &FirstMeaningfulPaintDetector::networkStableTimerFired) {}
 
 Document* FirstMeaningfulPaintDetector::document() {
-  return m_paintTiming->document();
+  return m_paintTiming->host();
 }
 
 // Computes "layout significance" (http://goo.gl/rytlPL) of a layout operation.