Derive the step base for an input element as (now) specified.

Source/core/html/forms/InputType.h

Index: Source/core/html/forms/InputType.h
diff --git a/Source/core/html/forms/InputType.h b/Source/core/html/forms/InputType.h
index 94ddda88791670b97f5b69af1b66fd538a07cb24..77320e0a06d87666c6449a1d7862b1e573d34f43 100644
--- a/Source/core/html/forms/InputType.h
+++ b/Source/core/html/forms/InputType.h
@@ -196,11 +196,13 @@ public:
     virtual Decimal findClosestTickMarkValue(const Decimal&);
     virtual void handleDOMActivateEvent(Event*);
 
-    // Parses the specified string for the type, and return
+    // Parses the first string argument for the input type, and return
     // the Decimal value for the parsing result if the parsing
-    // succeeds; Returns defaultValue otherwise. This function can
-    // return NaN or Infinity only if defaultValue is NaN or Infinity.
-    virtual Decimal parseToNumber(const String&, const Decimal& defaultValue) const;
+    // succeeds. If not, that parsing is attempted for the second
+    // argument. If that also fails, it returns defaultValue. This
+    // function can return NaN or Infinity only if defaultValue is NaN
+    // or Infinity.
+    virtual Decimal parseToNumber(const String&, const String&, const Decimal& defaultValue) const;

[sof, 2013/11/22 12:50:49]

FYI - I went back & forth a bit on whether or not to extend parseToNumber() like
this -- the alternative being to handle it in the createStepRange() methods for
the input types that have a step base. They were in the majority, hence I opted
for this, but could easily be convinced to address it differently.

[tkent, 2013/11/24 22:34:23]

I don't think adding another argument to parseToNumber is reasonable.
The new behavior looks out of scope of parseToNumber.

We should handle value attribute fallback in each of createStepRange, and we may
have an additional helper function.

[yosin_UTC9, 2013/11/25 01:26:41]

Agree with tkent@. It is confusing having alternative and default.
nit: Please put parameter name for const String&.

[sof, 2013/11/26 17:59:05]

Thanks, added a helper InputType::findStepBase(const Decimal&) instead &
reverted changes to parseToNumber().

(I did not give parseToNumber()'s first argument a name, however. Not sure there
is one that conveys considerable meaning.)

 
     // Parses the specified string for this InputType, and returns true if it
     // is successfully parsed. An instance pointed by the DateComponents*