add pan-x and pan-y support to CSS touch-action parsing.

Source/core/css/CSSComputedStyleDeclaration.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
@@ skipping 1524 matching lines @@
         return cssValuePool().createIdentifierValue(CSSValueBold);
     case FontWeight800:
         return cssValuePool().createIdentifierValue(CSSValue800);
     case FontWeight900:
         return cssValuePool().createIdentifierValue(CSSValue900);
     }
     ASSERT_NOT_REACHED();
     return cssValuePool().createIdentifierValue(CSSValueNormal);
 }
 
+static PassRefPtr<CSSValue> touchActionFlagsToCSSValue(TouchAction touchAction)
+{
+    RefPtr<CSSValueList> list = CSSValueList::createSpaceSeparated();
+    if (touchAction & TouchActionNone) {
+        ASSERT(!(list->length()));

[Rick Byers, 2013/12/12 15:30:35]

This is trivially true.

I think you can simplify these asserts by making them on the touchAction instead
of the list.  Eg. make this 'ASSERT(touchAction == touchActionNone))'.  Then I
think you can remove all the other ASSERTs - the only invalid combinations are
'None | PanX' and 'None | PanY', which will both be covered by the assert here.

[gnana, 2013/12/13 11:10:54]

Done.

+        list->append(cssValuePool().createIdentifierValue(CSSValueNone));
+    }
+    if (touchAction & TouchActionAuto) {

[Rick Byers, 2013/12/12 15:30:35]

The way you've defined it (which I think is reasonable) is that Auto isn't a
flag - it's the zero value.  So touchAction & TouchActionAuto is always false. 
So this should instead be 'if (touchAction == touchActionAuto)', and since it's
special perhaps put it first in the list of statements.  Sorry I missed this in
the previous review.

[gnana, 2013/12/13 11:10:54]

Done.

+        ASSERT(!(list->length()));
+        list->append(cssValuePool().createIdentifierValue(CSSValueAuto));
+    }
+    if (touchAction & TouchActionPanX) {
+        ASSERT(!(list->length() && !(list->hasValue(cssValuePool().createIdentifierValue(CSSValuePanY).get()))));
+        list->append(cssValuePool().createIdentifierValue(CSSValuePanX));
+    }
+    if (touchAction & TouchActionPanY) {
+        ASSERT(!(list->length() && !(list->hasValue(cssValuePool().createIdentifierValue(CSSValuePanX).get()))));
+        list->append(cssValuePool().createIdentifierValue(CSSValuePanY));
+    }
+
+    if (!list->length())

[Rick Byers, 2013/12/12 15:30:35]

When the above is fixed, you should be able to assert that the list is never
empty.

[gnana, 2013/12/13 11:10:54]

Done.

+        return cssValuePool().createIdentifierValue(CSSValueAuto);
+    return list.release();
+}
+
 static bool isLayoutDependent(CSSPropertyID propertyID, PassRefPtr<RenderStyle> style, RenderObject* renderer)
 {
     // Some properties only depend on layout in certain conditions which
     // are specified in the main switch statement below. So we can avoid
     // forcing layout in those conditions. The conditions in this switch
     // statement must remain in sync with the conditions in the main switch.
     // FIXME: Some of these cases could be narrowed down or optimized better.
     switch (propertyID) {
     case CSSPropertyBottom:
     case CSSPropertyGridDefinitionColumns:
@@ skipping 754 matching lines @@
             return cssValuePool().createValue(style->textSecurity());
         case CSSPropertyWebkitTextStrokeColor:
             return currentColorOrValidColor(*style, style->textStrokeColor());
         case CSSPropertyWebkitTextStrokeWidth:
             return zoomAdjustedPixelValue(style->textStrokeWidth(), *style);
         case CSSPropertyTextTransform:
             return cssValuePool().createValue(style->textTransform());
         case CSSPropertyTop:
             return valueForPositionOffset(*style, CSSPropertyTop, renderer, m_node->document().renderView());
         case CSSPropertyTouchAction:
-            return cssValuePool().createValue(style->touchAction());
+            return touchActionFlagsToCSSValue(style->touchAction());
         case CSSPropertyTouchActionDelay:
             return cssValuePool().createValue(style->touchActionDelay());
         case CSSPropertyUnicodeBidi:
             return cssValuePool().createValue(style->unicodeBidi());
         case CSSPropertyVerticalAlign:
             switch (style->verticalAlign()) {
                 case BASELINE:
                     return cssValuePool().createIdentifierValue(CSSValueBaseline);
                 case MIDDLE:
                     return cssValuePool().createIdentifierValue(CSSValueMiddle);
@@ skipping 900 matching lines @@
     static const CSSPropertyID propertiesAfterSlashSeperator[3] = { CSSPropertyBackgroundSize, CSSPropertyBackgroundOrigin,
                                                                     CSSPropertyBackgroundClip };
 
     RefPtr<CSSValueList> list = CSSValueList::createSlashSeparated();
     list->append(valuesForShorthandProperty(StylePropertyShorthand(CSSPropertyBackground, propertiesBeforeSlashSeperator, WTF_ARRAY_LENGTH(propertiesBeforeSlashSeperator))));
     list->append(valuesForShorthandProperty(StylePropertyShorthand(CSSPropertyBackground, propertiesAfterSlashSeperator, WTF_ARRAY_LENGTH(propertiesAfterSlashSeperator))));
     return list.release();
 }
 
 } // namespace WebCore