Fix size of rotated text with FreeType.

src/ports/SkFontHost_win.cpp

Index: src/ports/SkFontHost_win.cpp
===================================================================
--- src/ports/SkFontHost_win.cpp	(revision 14081)
+++ src/ports/SkFontHost_win.cpp	(working copy)
@@ -16,6 +16,7 @@
 #include "SkGlyph.h"
 #include "SkHRESULT.h"
 #include "SkMaskGamma.h"
+#include "SkMatrix22.h"
 #include "SkOTTable_maxp.h"
 #include "SkOTTable_name.h"
 #include "SkOTUtils.h"
@@ -636,34 +637,9 @@
     fRec.getSingleMatrix(&A);
     A.mapPoints(&h, 1);
 
-    // Find the Given's matrix [[c, -s],[s, c]] which rotates the baseline vector h
-    // (where the baseline is mapped to) to the positive horizontal axis.
-    const SkScalar& a = h.fX;
-    const SkScalar& b = h.fY;
-    SkScalar c, s;
-    if (0 == b) {
-        c = SkDoubleToScalar(_copysign(SK_Scalar1, a));
-        s = 0;
-    } else if (0 == a) {
-        c = 0;
-        s = SkDoubleToScalar(-_copysign(SK_Scalar1, b));
-    } else if (SkScalarAbs(b) > SkScalarAbs(a)) {
-        SkScalar t = a / b;
-        SkScalar u = SkDoubleToScalar(_copysign(SkScalarSqrt(SK_Scalar1 + t*t), b));
-        s = -1 / u;
-        c = -s * t;
-    } else {
-        SkScalar t = b / a;
-        SkScalar u = SkDoubleToScalar(_copysign(SkScalarSqrt(SK_Scalar1 + t*t), a));
-        c = 1 / u;
-        s = -c * t;
-    }
-
-    // G is the Given's Matrix for A (rotational matrix such that GA[0][1] == 0).
+    // G is the Givens Matrix for A (rotational matrix where GA[0][1] == 0).
     SkMatrix G;
-    G.setAll(c, -s, 0,
-             s,  c, 0,
-             0,  0, SkScalarToPersp(SK_Scalar1));
+    SkComputeGivensRotation(h, &G);
 
     // GA is the matrix A with rotation removed.
     SkMatrix GA(G);