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

Source/core/css/CSSComputedStyleDeclaration.cpp

Index: Source/core/css/CSSComputedStyleDeclaration.cpp
diff --git a/Source/core/css/CSSComputedStyleDeclaration.cpp b/Source/core/css/CSSComputedStyleDeclaration.cpp
old mode 100644
new mode 100755
index 82d0c741688d8cd2ba4159284ff508c06120f53c..72d69c23f2284e0e7faaa1b29e53f1801a0db8ed
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -1542,6 +1542,31 @@ static PassRefPtr<CSSPrimitiveValue> valueForFontWeight(RenderStyle& style)
     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
@@ -2316,7 +2341,7 @@ PassRefPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValue(CSSPropert
         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: