Prevent LayoutTest setting -1 page scale factor.

third_party/WebKit/Source/core/frame/PageScaleConstraints.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
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@@ skipping 40 matching lines @@
         minimumScale = other.minimumScale;
     if (other.maximumScale != -1)
         maximumScale = other.maximumScale;
     if (!other.layoutSize.isZero())
         layoutSize = other.layoutSize;
     clampAll();
 }
 
 float PageScaleConstraints::clampToConstraints(float pageScaleFactor) const
 {
-    if (pageScaleFactor == -1)

[bokan, 2016/09/19 19:01:21]

I don't think this is the right way to fix this. -1 is used as an "unset" value
here. In the case of initial scale, we need to differentiate between a set and
unset initial scale.

The actual page scale factor should never be -1 so we shouldn't ever call into
this method with the real page scale factor at -1. The bug is somewhere higher
up in the call stack.

-        return pageScaleFactor;
     if (minimumScale != -1)
         pageScaleFactor = std::max(pageScaleFactor, minimumScale);
     if (maximumScale != -1)
         pageScaleFactor = std::min(pageScaleFactor, maximumScale);
     return pageScaleFactor;
 }
 
 void PageScaleConstraints::clampAll()
 {
     if (minimumScale != -1 && maximumScale != -1)
@@ skipping 25 matching lines @@
 
 bool PageScaleConstraints::operator==(const PageScaleConstraints& other) const
 {
     return layoutSize == other.layoutSize
         && initialScale == other.initialScale
         && minimumScale == other.minimumScale
         && maximumScale == other.maximumScale;
 }
 
 } // namespace blink