Bug 1074944 - Add Inverse functions on Matrix and Matrix4x4. r=Bas

gfx/2d/Matrix.h

@@ -11,6 +11,7 @@
 #include "Point.h"
 #include <math.h>
 #include "mozilla/Attributes.h"
+#include "mozilla/DebugOnly.h"
 
 namespace mozilla {
 namespace gfx {
@@ -186,6 +187,14 @@ public:
     return true;
   }
 
+  Matrix Inverse() const
+  {
+    Matrix clone = *this;
+    DebugOnly<bool> inverted = clone.Invert();
+    MOZ_ASSERT(inverted, "Attempted to get the inverse of a non-invertible matrix");
+    return clone;
+  }
+
   Float Determinant() const
   {
     return _11 * _22 - _12 * _21;
@@ -671,6 +680,14 @@ public:
 
   bool Invert();
 
+  Matrix4x4 Inverse() const
+  {
+    Matrix4x4 clone = *this;
+    DebugOnly<bool> inverted = clone.Invert();
+    MOZ_ASSERT(inverted, "Attempted to get the inverse of a non-invertible matrix");
+    return clone;
+  }
+
   void Normalize()
   {
       for (int i = 0; i < 4; i++) {