Clear mutable inline style when it is empty.

Source/core/css/VariablesIterator.cpp

Index: Source/core/css/VariablesIterator.cpp
diff --git a/Source/core/css/VariablesIterator.cpp b/Source/core/css/VariablesIterator.cpp
index 9b229f77532aa23a268b6bd4496925df9a835d59..c2e92cce2ab2b22a59508f6d959b5f8215e70b61 100644
--- a/Source/core/css/VariablesIterator.cpp
+++ b/Source/core/css/VariablesIterator.cpp
@@ -23,12 +23,13 @@
 #include "RuntimeEnabledFeatures.h"
 #include "core/css/CSSVariableValue.h"
 #include "core/css/StylePropertySet.h"
+#include "core/dom/Element.h"
 
 namespace WebCore {
 
-PassRefPtr<VariablesIterator> VariablesIterator::create(MutableStylePropertySet* propertySet)
+void AbstractVariablesIterator::initRemainingNames(

[eseidel, 2013/12/23 21:30:23]

Could this just be part of the AbstractVariablesIterator constructor?  If not,
is there a way we can ASSERT when implementors fail to call this method?

[chrishtr, 2013/12/23 22:06:46]

I think it can, per your other comment. Will fix.

[chrishtr, 2013/12/23 22:34:20]

Done.

+    const StylePropertySet* propertySet, AbstractVariablesIterator* iterator)
 {
-    ASSERT(RuntimeEnabledFeatures::cssVariablesEnabled());
     const size_t propertyCount = propertySet->propertyCount();
     size_t variableCount = 0;
     Vector<AtomicString> remainingNames(propertyCount);
@@ -37,11 +38,17 @@ PassRefPtr<VariablesIterator> VariablesIterator::create(MutableStylePropertySet*
         if (property.id() == CSSPropertyVariable)
             remainingNames[variableCount++] = toCSSVariableValue(property.value())->name();
     }
+    // FIXME: Make use of the Vector move constructor when rvalues are supported on all platforms.
     remainingNames.shrink(variableCount);
 
-    RefPtr<VariablesIterator> iterator = adoptRef(new VariablesIterator(propertySet));
-    // FIXME: Make use of the Vector move constructor when rvalues are supported on all platforms.
     iterator->takeRemainingNames(remainingNames);
+}
+
+PassRefPtr<VariablesIterator> VariablesIterator::create(MutableStylePropertySet* propertySet)
+{
+    ASSERT(RuntimeEnabledFeatures::cssVariablesEnabled());
+    RefPtr<VariablesIterator> iterator = adoptRef(new VariablesIterator(propertySet));
+    AbstractVariablesIterator::initRemainingNames(propertySet, iterator.get());

[eseidel, 2013/12/23 21:30:23]

As I commented in a previous pass, it's uncommon to have ::create() do anything
besides wrap the new calls in an adoptRef.  That said, if this needs to be done
this way it's totally fine.  I would add a comment in the header next to
initRemainingNames() that all subclasses must call it, etc.

[chrishtr, 2013/12/23 22:34:20]

Done.

     return iterator.release();
 }