Prevent LayoutTest setting -1 page scale factor.

third_party/WebKit/Source/core/testing/Internals.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 1860 matching lines @@
     if (!document || !document->page()) {
         exceptionState.throwDOMException(InvalidAccessError, document ? "The document's page cannot be retrieved." : "No context document can be obtained.");
         return 0;
     }
     Page* page = document->page();
     return page->frameHost().visualViewport().pageScale();
 }
 
 void Internals::setPageScaleFactor(float scaleFactor, ExceptionState& exceptionState)
 {
+    // -1 is the initial value of page scale factor in blink, it should never be
+    // set by external methods.
+    if (scaleFactor == -1)

[bokan, 2016/09/20 17:32:09]

it's not the initial value. It's a value used by the various limits (minimum,
maximum, initial-scale) but never page scale factor. Just make this `if
(scaleFactor <= 0) return;`, no need for a comment.

[sunxd, 2016/09/20 17:47:10]

Done.

+        return;
     Document* document = contextDocument();
     if (!document || !document->page()) {
         exceptionState.throwDOMException(InvalidAccessError, document ? "The document's page cannot be retrieved." : "No context document can be obtained.");
         return;
     }
     Page* page = document->page();
     page->frameHost().visualViewport().setScale(scaleFactor);
 }
 
 void Internals::setPageScaleFactorLimits(float minScaleFactor, float maxScaleFactor, ExceptionState& exceptionState)
@@ skipping 779 matching lines @@
 
     return ClientRect::create(FloatRect(node->layoutObject()->visualRect()));
 }
 
 void Internals::crash()
 {
     CHECK(false) << "Intentional crash";
 }
 
 } // namespace blink