constructor: Don't round unless we have to

Unless `significantDigits` or `fractionDigits` is set, we
don't need to round. Let's just keep the unrounded
mathematical value, and round only if necessary.

Author: jessealama

spec.emu

@@ -160,10 +160,7 @@ location: https://github.com/tc39/proposal-measure/
             1. If _roundingMode_ is *"ceil"*, set _reverseRoundingMode_ to *"floor"*.
             1. Let _d_ be RoundToAmountDomain(–_v_, _reverseRoundingMode_).
             1. Return –_d_.
-          1. Let _e_ be the unique integer such that 10<sup>_e_</sup> ≤ _v_ < 10<sup>_e_+1</sup>.
-          1. Let _m_ be _v_ × 10<sup>–_e_</sup>.
-          1. Let _rounded_ be ApplyRoundingModeToPositive(_m_, _roundingMode_).
-          1. Return _rounded_ × 10<sup>_e_</sup>.
+          1. Return ApplyRoundingModeToPositive(_m_, _roundingMode_).
         </emu-alg>
       </emu-clause>
 
@@ -260,6 +257,7 @@ location: https://github.com/tc39/proposal-measure/
         1. Otherwise, if _x_ is a String, set _toParse_ to _x_.
         1. If _toParse_ is not a String, throw a *TypeError* exception.
         1. If _toParse_ is in « *"NaN"*, *"Infinity"*, *"-Infinity"* », throw a *RangeError* exception.
+        1. Set _opts_ to GetOptionsObject(_opts_).
         1. Let _roundingMode_ be ? GetOption(_opts_, *"roundingMode"*, ~string~, « *"ceil"*, *"floor"*, *"expand"*, *"trunc"*, *"halfCeil"*, *"halfFloor"*, *"halfExpand"*, *"halfTrunc"*, *"halfEven"* », *"halfEven"*).
         1. Let _unit_ be ? GetOption(_opts_, *"unit"*, ~string~, ~empty~, *undefined*).
         1. Let _currency_ be ? GetOption(_opts_, *"currency"*, ~string~, ~empty~, *undefined*).
@@ -279,19 +277,19 @@ location: https://github.com/tc39/proposal-measure/
         1. Let _parseResult_ be ParseText(_toParse_, |StrDecimalLiteral|).
         1. If _parseResult_ is a List of errors, throw a *SyntaxError* exception.
         1. Let _amountValue_ be ? StringDecimalValue of _parseResult_.
-        1. Let _roundedAmountValue_ be RoundToAmountDomain(_amountValue_, _roundingMode_).
+        1. Let _roundedValue_ be _amountValue_.
         1. If both _significantDigits_ and _fractionDigits_ are *undefined*, then
           1. Set _significantDigits_ to CountSignificantDigits(_toParse_).
           1. Set _fractionDigits_ to CountFractionDigits(_toParse_).
         1. Else if _significantDigits_ is *undefined*, then
-          1. Set _roundedAmountValue_ be RoundToFractionalDigits(_amountValue_, _fractionDigits_, _roundingMode_).
-          1. Let _digitStr_ be the unique decimal string representation of _roundedAmountValue_ without leading zeroes.
+          1. Set _roundedValue_ be RoundToFractionalDigits(_amountValue_, _fractionDigits_, _roundingMode_).
+          1. Let _digitStr_ be the unique decimal string representation of _roundedValue_ without leading zeroes.
           1. Set _significantDigits_ to CountSignificantDigits(_digitStr_).
         1. Otherwise:
-          1. Set _roundedAmountValue_ be RoundToSignificantDigits(_amountValue_, _significantDigits_, _roundingMode_).
-          1. Let _digitStr_ be the unique decimal string representation of _roundedAmountValue_ without leading zeroes.
+          1. Set _roundedValue_ be RoundToSignificantDigits(_amountValue_, _significantDigits_, _roundingMode_).
+          1. Let _digitStr_ be the unique decimal string representation of _roundedValue_ without leading zeroes.
           1. Set _fractionDigits_ to CountFractionDigits(_digitStr_).
-        1. Set _O_.[[Value]] to _roundedAmountValue_.
+        1. Set _O_.[[Value]] to _roundedValue_.
         1. Set _O_.[[SignificantDigits]] to _significantDigits_.
         1. Set _O_.[[FractionDigits]] to _fractionDigits_.
         1. If _unit_ is a String, set _O_.[[Unit]] to toLowercase(StringToCodePoints(_unit_)).