Bug 1062406 - Part 1 - Change x and y parameters of window.scroll* CSSOM-View DOM calls from double to unrestricted double. r=bz

- WebIDL updated so that x and y parameters of window.scroll, window.scrollTo,
  and window.ScrollBy are changed from "double" to "unrestricted double".
- Implemented mozilla::ToZeroIfNonfinite
- Updated nsGlobalWindow::Scroll, ScrollTo, and ScrollBy methods so that they
  replace non-finite numbers with 0.

dom/base/nsGlobalWindow.cpp

@@ -7129,17 +7129,23 @@ nsGlobalWindow::GetTopWindowRoot()
 }
 
 void
-nsGlobalWindow::Scroll(int32_t aXScroll, int32_t aYScroll,
+nsGlobalWindow::Scroll(double aXScroll, double aYScroll,
                        const ScrollOptions& aOptions)
 {
-  ScrollTo(CSSIntPoint(aXScroll, aYScroll), aOptions);
+  // Convert -Inf, Inf, and NaN to 0; otherwise, convert by C-style cast.
+  CSSIntPoint scrollPos(mozilla::ToZeroIfNonfinite(aXScroll),
+                        mozilla::ToZeroIfNonfinite(aYScroll));
+  ScrollTo(scrollPos, aOptions);
 }
 
 void
-nsGlobalWindow::ScrollTo(int32_t aXScroll, int32_t aYScroll,
+nsGlobalWindow::ScrollTo(double aXScroll, double aYScroll,
                          const ScrollOptions& aOptions)
 {
-  ScrollTo(CSSIntPoint(aXScroll, aYScroll), aOptions);
+  // Convert -Inf, Inf, and NaN to 0; otherwise, convert by C-style cast.
+  CSSIntPoint scrollPos(mozilla::ToZeroIfNonfinite(aXScroll),
+                        mozilla::ToZeroIfNonfinite(aYScroll));
+  ScrollTo(scrollPos, aOptions);
 }
 
 NS_IMETHODIMP
@@ -7196,19 +7202,20 @@ nsGlobalWindow::ScrollBy(int32_t aXScrollDif, int32_t aYScrollDif)
 }
 
 void
-nsGlobalWindow::ScrollBy(int32_t aXScrollDif, int32_t aYScrollDif,
+nsGlobalWindow::ScrollBy(double aXScrollDif, double aYScrollDif,
                          const ScrollOptions& aOptions)
 {
   FlushPendingNotifications(Flush_Layout);
   nsIScrollableFrame *sf = GetScrollFrame();
 
   if (sf) {
-    CSSIntPoint scrollPos =
-      sf->GetScrollPositionCSSPixels() + CSSIntPoint(aXScrollDif, aYScrollDif);
+    // Convert -Inf, Inf, and NaN to 0; otherwise, convert by C-style cast.
+    CSSIntPoint scrollDif(mozilla::ToZeroIfNonfinite(aXScrollDif),
+                          mozilla::ToZeroIfNonfinite(aYScrollDif));
     // It seems like it would make more sense for ScrollBy to use
     // SMOOTH mode, but tests seem to depend on the synchronous behaviour.
     // Perhaps Web content does too.
-    ScrollTo(scrollPos, aOptions);
+    ScrollTo(sf->GetScrollPositionCSSPixels() + scrollDif, aOptions);
   }
 }
 

dom/base/nsGlobalWindow.h

@@ -897,11 +897,11 @@ public:
                 mozilla::ErrorResult& aError);
   void ResizeBy(int32_t aWidthDif, int32_t aHeightDif,
                 mozilla::ErrorResult& aError);
-  void Scroll(int32_t aXScroll, int32_t aYScroll,
+  void Scroll(double aXScroll, double aYScroll,
               const mozilla::dom::ScrollOptions& aOptions);
-  void ScrollTo(int32_t aXScroll, int32_t aYScroll,
+  void ScrollTo(double aXScroll, double aYScroll,
                 const mozilla::dom::ScrollOptions& aOptions);
-  void ScrollBy(int32_t aXScrollDif, int32_t aYScrollDif,
+  void ScrollBy(double aXScrollDif, double aYScrollDif,
                 const mozilla::dom::ScrollOptions& aOptions);
   void ScrollByLines(int32_t numLines,
                      const mozilla::dom::ScrollOptions& aOptions);

dom/webidl/Window.webidl

@@ -179,9 +179,9 @@ partial interface Window {
   //[Throws] readonly attribute double pageXOffset;
   //[Throws] readonly attribute double scrollY;
   //[Throws] readonly attribute double pageYOffset;
-  void scroll(double x, double y, optional ScrollOptions options);
-  void scrollTo(double x, double y, optional ScrollOptions options);
-  void scrollBy(double x, double y, optional ScrollOptions options);
+  void scroll(unrestricted double x, unrestricted double y, optional ScrollOptions options);
+  void scrollTo(unrestricted double x, unrestricted double y, optional ScrollOptions options);
+  void scrollBy(unrestricted double x, unrestricted double y, optional ScrollOptions options);
   [Replaceable, Throws] readonly attribute long scrollX;
   [Throws] readonly attribute long pageXOffset;
   [Replaceable, Throws] readonly attribute long scrollY;

mfbt/FloatingPoint.h

@@ -187,6 +187,17 @@ IsNegativeZero(T aValue)
   return bits == Traits::kSignBit;
 }
 
+/**
+ * Returns 0 if a float/double is NaN or infinite;
+ * otherwise, the float/double is returned.
+ */
+template<typename T>
+static MOZ_ALWAYS_INLINE T
+ToZeroIfNonfinite(T aValue)
+{
+  return IsFinite(aValue) ? aValue : 0;
+}
+
 /**
  * Returns the exponent portion of the float/double.
  *