Fix dom/ranges/Range-compareBoundaryPoints.html on ARM

The how parameter is defined as unsigned short in WebIDL. The
generated bindings end up calling ToSmallerUInt in V8BindingForCore.cpp.
The final cast in this method seems to hit an ARM specific issue [1].
To fix this static cast to int64_t before static casting to the unsigned type.

[1] http://www.embeddeduse.com/2013/08/25/casting-a-negative-float-to-an-unsigned-int/

Bug: 823812

Cq-Include-Trybots: master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I90c733185b8325984e004224dd72176840d1794e
Reviewed-on: https://chromium-review.googlesource.com/970901Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Rob Buis <rob.buis@samsung.com>
Cr-Commit-Position: refs/heads/master@{#545078}

third_party/WebKit/LayoutTests/SmokeTests

@@ -185,6 +185,7 @@ external/wpt/dom/nodes/Document-contentType/contentType/createHTMLDocument.html
 external/wpt/dom/nodes/Node-lookupPrefix.xhtml
 external/wpt/domparsing/innerhtml-03.xhtml
 external/wpt/domparsing/innerhtml-04.html
+external/wpt/dom/ranges/Range-compareBoundaryPoints.html
 external/wpt/dom/ranges/Range-constructor.html
 external/wpt/dom/traversal/NodeFilter-constants.html
 external/wpt/dom/traversal/TreeWalker-walking-outside-a-tree.html

third_party/WebKit/Source/bindings/core/v8/V8BindingForCore.cpp

@@ -43,6 +43,7 @@
 #include "bindings/core/v8/WindowProxy.h"
 #include "bindings/core/v8/WorkerOrWorkletScriptController.h"
 #include "bindings/core/v8/custom/V8CustomXPathNSResolver.h"
+#include "build/build_config.h"
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/QualifiedName.h"
@@ -256,9 +257,14 @@ static inline T ToSmallerUInt(v8::Isolate* isolate,
   if (std::isinf(number_value))
     return 0;
 
-  number_value =
-      number_value < 0 ? -floor(fabs(number_value)) : floor(fabs(number_value));
-  return static_cast<T>(fmod(number_value, LimitsTrait::kNumberOfValues));
+  // Confine number to (-kNumberOfValues, kNumberOfValues).
+  double number = fmod(trunc(number_value), LimitsTrait::kNumberOfValues);
+
+  // Adjust range to [0, kNumberOfValues).
+  if (number < 0)
+    number += LimitsTrait::kNumberOfValues;
+
+  return static_cast<T>(number);
 }
 
 int8_t ToInt8(v8::Isolate* isolate,