[PathKit] Add cubicYFromX


Docs-Preview: https://skia.org/?cl=152385
Bug: skia:8216
Change-Id: I0020e8d2d4e6e7c7de5c71ddf923a618659cde2c
Reviewed-on: https://skia-review.googlesource.com/152385
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
diff --git a/modules/pathkit/externs.js b/modules/pathkit/externs.js
index 9116254..c6c5fc9 100644
--- a/modules/pathkit/externs.js
+++ b/modules/pathkit/externs.js
@@ -27,6 +27,9 @@
 	_FromCmds: function(ptr, size) {},
 	loadCmdsTypedArray: function(arr) {},
 	FromCmds: function(arr) {},
+	_SkCubicMap: function(cp1, cp2) {},
+	cubicYFromX: function(cpx1, cpy1, cpx2, cpy2, X) {},
+	cubicPtFromT: function(cpx1, cpy1, cpx2, cpy2, T) {},
 
 	HEAPF32: {},
 
@@ -70,6 +73,10 @@
 StrokeOpts.prototype.cap;
 StrokeOpts.prototype.join;
 
+// Define CubicMap object
+var CubicMap = {};
+CubicMap.prototype.computeYFromX = function(x) {};
+CubicMap.prototype.computePtFromT = function(t) {};
 
 
 // For whatever reason, the closure compiler thinks it can rename some of our