Fix problems with flakes in SVG LayoutTests by reordering arithmetic.

Source/core/svg/SVGLengthContext.cpp

Index: Source/core/svg/SVGLengthContext.cpp
diff --git a/Source/core/svg/SVGLengthContext.cpp b/Source/core/svg/SVGLengthContext.cpp
index 4bffd9cae72f1001a0be6c2596c167ac4e3d2c4d..c72611e191ae10752f41fce7780b4357ab67853f 100644
--- a/Source/core/svg/SVGLengthContext.cpp
+++ b/Source/core/svg/SVGLengthContext.cpp
@@ -52,10 +52,10 @@ FloatRect SVGLengthContext::resolveRectangle(const SVGElement* context, SVGUnitT
     if (type != SVGUnitTypes::SVG_UNIT_TYPE_USERSPACEONUSE && !viewport.isEmpty()) {
         const FloatSize& viewportSize = viewport.size();
         return FloatRect(
-            convertValueFromPercentageToUserUnits(x->valueAsPercentage(), x->unitMode(), viewportSize) + viewport.x(),
-            convertValueFromPercentageToUserUnits(y->valueAsPercentage(), y->unitMode(), viewportSize) + viewport.y(),
-            convertValueFromPercentageToUserUnits(width->valueAsPercentage(), width->unitMode(), viewportSize),
-            convertValueFromPercentageToUserUnits(height->valueAsPercentage(), height->unitMode(), viewportSize));
+            convertValueFromPercentageToUserUnits(*x, viewportSize) + viewport.x(),
+            convertValueFromPercentageToUserUnits(*y, viewportSize) + viewport.y(),
+            convertValueFromPercentageToUserUnits(*width, viewportSize),
+            convertValueFromPercentageToUserUnits(*height, viewportSize));
     }
 
     SVGLengthContext lengthContext(context);
@@ -102,7 +102,7 @@ float SVGLengthContext::convertValueToUserUnits(float value, SVGLengthMode mode,
     case LengthTypePX:
         return value;
     case LengthTypePercentage:
-        return convertValueFromPercentageToUserUnits(value / 100, mode, exceptionState);
+        return convertValueFromPercentageToUserUnits(value, mode, exceptionState) / 100;
     case LengthTypeEMS:
         return convertValueFromEMSToUserUnits(value, exceptionState);
     case LengthTypeEXS:
@@ -201,6 +201,27 @@ float SVGLengthContext::convertValueFromPercentageToUserUnits(float value, SVGLe
     return 0;
 }
 
+float SVGLengthContext::convertValueFromPercentageToUserUnits(const SVGLength& value, const FloatSize& viewportSize)
+{
+    float resultValue;
+    switch (value.unitMode()) {
+    default:
+        ASSERT_NOT_REACHED();

[fs, 2015/01/22 12:37:36]

I'd prefer to structure this new function like the previous - i.e. tail-calls
and ASSERT_NOT_REACHED() outside the switch.

[Daniel Bratell, 2015/01/22 13:13:44]

Ok.

I do like this structure though because it generates more efficient code and
won't contain dummy return values put there to silence compilers, but instead
causing confusion in code analyzers.

[fs, 2015/01/22 14:06:35]

Well saying that it generates better code is a bold statement IMO =) (plenty of
things to fubar in this version too.) And the dummy return value is instead
replaced by a dummy switch-case. (Also, if ASSERT_NOT_REACHED is implemented in
a meaningful way, that edge will be dead in practice.)

+        // Fall through.
+    case LengthModeWidth:
+        resultValue = value.scaleByPercentage(viewportSize.width());
+        break;
+    case LengthModeHeight:
+        resultValue = value.scaleByPercentage(viewportSize.height());
+        break;
+    case LengthModeOther:
+        resultValue = value.scaleByPercentage(sqrtf(viewportSize.diagonalLengthSquared() / 2));
+        break;
+    };
+
+    return resultValue;
+}
+
 static inline RenderStyle* renderStyleForLengthResolving(const SVGElement* context)
 {
     if (!context)