[WIP] Supporting arm_neon_optional flag for blink platform.

Source/platform/graphics/cpu/arm/filters/FECompositeArithmeticNEON.h

Index: Source/platform/graphics/cpu/arm/filters/FECompositeArithmeticNEON.h
diff --git a/Source/platform/graphics/cpu/arm/filters/FECompositeArithmeticNEON.h b/Source/platform/graphics/cpu/arm/filters/FECompositeArithmeticNEON.h
index bbf793e5ec2628ebfb75f23af25eb68e90bbdad0..a196e201810aef6e85d6a57384702124122650fd 100644
--- a/Source/platform/graphics/cpu/arm/filters/FECompositeArithmeticNEON.h
+++ b/Source/platform/graphics/cpu/arm/filters/FECompositeArithmeticNEON.h
@@ -72,24 +72,26 @@ inline void FEComposite::computeArithmeticPixelsNeon(unsigned char* source, unsi
     }
 }
 
-inline void FEComposite::platformArithmeticNeon(unsigned char* source, unsigned char* destination,
-    unsigned pixelArrayLength, float k1, float k2, float k3, float k4)
+inline void FEComposite::arithmeticSoftwareNEON(unsigned char* source, unsigned char* destination,
+    int pixelArrayLength, float k1, float k2, float k3, float k4)
 {
+    ASSERT(!(pixelArrayLength & 0x3));
+
     if (!k4) {
         if (!k1) {
-            computeArithmeticPixelsNeon<0, 0>(source, destination, pixelArrayLength, k1, k2, k3, k4);
+            computeArithmeticPixelsNeon<0, 0>(source, destination, static_cast<unsigned>(pixelArrayLength), k1, k2, k3, k4);
             return;
         }
 
-        computeArithmeticPixelsNeon<1, 0>(source, destination, pixelArrayLength, k1, k2, k3, k4);
+        computeArithmeticPixelsNeon<1, 0>(source, destination, static_cast<unsigned>(pixelArrayLength), k1, k2, k3, k4);
         return;
     }
 
     if (!k1) {
-        computeArithmeticPixelsNeon<0, 1>(source, destination, pixelArrayLength, k1, k2, k3, k4);
+        computeArithmeticPixelsNeon<0, 1>(source, destination, static_cast<unsigned>(pixelArrayLength), k1, k2, k3, k4);
         return;
     }
-    computeArithmeticPixelsNeon<1, 1>(source, destination, pixelArrayLength, k1, k2, k3, k4);
+    computeArithmeticPixelsNeon<1, 1>(source, destination, static_cast<unsigned>(pixelArrayLength), k1, k2, k3, k4);
 }
 
 } // namespace blink