Fix narrowing conversion errors from r11986

Although this function only gets used for SkMScalar=float, it gets
compiled in when SkMScalar=double.

R=epoger@google.com
BUG=1764

Author: enne@chromium.org

Review URL: https://codereview.chromium.org/49463005

git-svn-id: http://skia.googlecode.com/svn/trunk@11991 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkMatrix44.cpp b/src/utils/SkMatrix44.cpp
index a598e52..37ab8db 100644
--- a/src/utils/SkMatrix44.cpp
+++ b/src/utils/SkMatrix44.cpp
@@ -819,7 +819,10 @@
         float sx = src2[0];
         float sy = src2[1];
         for (int i = 0; i < 4; i++) {
-            dst4[i] = mat[0][i] * sx + mat[1][i] * sy + mat[3][i];
+            dst4[i] =
+                SkMScalarToFloat(mat[0][i]) * sx +
+                SkMScalarToFloat(mat[1][i]) * sy +
+                SkMScalarToFloat(mat[3][i]);
         }
         src2 += 2;
         dst4 += 4;