Reset to initial page scale in additional scenarios.

Source/web/PageScaleConstraintsSet.cpp

Index: Source/web/PageScaleConstraintsSet.cpp
diff --git a/Source/web/PageScaleConstraintsSet.cpp b/Source/web/PageScaleConstraintsSet.cpp
index 582c27fce1427446acfd83a516d60c0ab7d01569..15f6e824d27c58167a67bcd1e952c71d0b2dc37d 100644
--- a/Source/web/PageScaleConstraintsSet.cpp
+++ b/Source/web/PageScaleConstraintsSet.cpp
@@ -66,11 +66,17 @@ void PageScaleConstraintsSet::setUserAgentConstraints(const PageScaleConstraints
     m_constraintsDirty = true;
 }
 
+PageScaleConstraints PageScaleConstraintsSet::computeConstraintsStack() const
+{
+    PageScaleConstraints constraints = defaultConstraints();
+    constraints.overrideWith(m_pageDefinedConstraints);
+    constraints.overrideWith(m_userAgentConstraints);
+    return constraints;
+}
+
 void PageScaleConstraintsSet::computeFinalConstraints()
 {
-    m_finalConstraints = defaultConstraints();
-    m_finalConstraints.overrideWith(m_pageDefinedConstraints);
-    m_finalConstraints.overrideWith(m_userAgentConstraints);
+    m_finalConstraints = computeConstraintsStack();
 
     m_constraintsDirty = false;
 }
@@ -89,12 +95,12 @@ void PageScaleConstraintsSet::setNeedsReset(bool needsReset)
 
 void PageScaleConstraintsSet::didChangeContentsSize(IntSize contentsSize, float pageScaleFactor)
 {
-    // If a large fixed-width element expanded the size of the document
-    // late in loading and our initial scale is not constrained, reset the
-    // page scale factor to the new minimum scale.
+    // If a large fixed-width element expanded the size of the document late in
+    // loading and our initial scale is not set (or set to be less than the last
+    // minimum scale), reset the page scale factor to the new initial scale.
     if (contentsSize.width() > m_lastContentsWidth
         && pageScaleFactor == finalConstraints().minimumScale
-        && userAgentConstraints().initialScale == -1 && pageDefinedConstraints().initialScale == -1)
+        && computeConstraintsStack().initialScale < finalConstraints().minimumScale)
         setNeedsReset(true);
 
     m_constraintsDirty = true;
@@ -168,9 +174,6 @@ void PageScaleConstraintsSet::adjustForAndroidWebViewQuirks(const ViewportDescri
         }
     }
 
-    if (oldInitialScale != m_pageDefinedConstraints.initialScale && m_pageDefinedConstraints.initialScale != -1)
-        setNeedsReset(true);
-
     if (adjustedLayoutSizeWidth != m_pageDefinedConstraints.layoutSize.width()) {
         ASSERT(m_pageDefinedConstraints.layoutSize.width() > 0);
         float adjustedLayoutSizeHeight = (adjustedLayoutSizeWidth * m_pageDefinedConstraints.layoutSize.height()) / m_pageDefinedConstraints.layoutSize.width();