Update SkLightingShader to support rotation

src/effects/SkPoint3.cpp

-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "SkPoint3.h"
-
-// Returns the square of the Euclidian distance to (x,y,z).
-static inline float get_length_squared(float x, float y, float z) {
-    return x * x + y * y + z * z;
-}
-
-// Calculates the square of the Euclidian distance to (x,y,z) and stores it in
-// *lengthSquared.  Returns true if the distance is judged to be "nearly zero".
-//
-// This logic is encapsulated in a helper method to make it explicit that we
-// always perform this check in the same manner, to avoid inconsistencies
-// (see http://code.google.com/p/skia/issues/detail?id=560 ).
-static inline bool is_length_nearly_zero(float x, float y, float z, float *lengthSquared) {
-    *lengthSquared = get_length_squared(x, y, z);
-    return *lengthSquared <= (SK_ScalarNearlyZero * SK_ScalarNearlyZero);
-}
-
-SkScalar SkPoint3::Length(SkScalar x, SkScalar y, SkScalar z) {
-    float magSq = get_length_squared(x, y, z);
-    if (SkScalarIsFinite(magSq)) {
-        return sk_float_sqrt(magSq);
-    } else {
-        double xx = x;
-        double yy = y;
-        double zz = z;
-        return (float)sqrt(xx * xx + yy * yy + zz * zz);
-    }
-}
-
-/*
- *  We have to worry about 2 tricky conditions:
- *  1. underflow of magSq (compared against nearlyzero^2)
- *  2. overflow of magSq (compared w/ isfinite)
- *
- *  If we underflow, we return false. If we overflow, we compute again using
- *  doubles, which is much slower (3x in a desktop test) but will not overflow.
- */
-bool SkPoint3::normalize() {
-    float magSq;
-    if (is_length_nearly_zero(fX, fY, fZ, &magSq)) {
-        this->set(0, 0, 0);
-        return false;
-    }
-
-    float scale;
-    if (SkScalarIsFinite(magSq)) {
-        scale = 1.0f / sk_float_sqrt(magSq);
-    } else {
-        // our magSq step overflowed to infinity, so use doubles instead.
-        // much slower, but needed when x, y or z is very large, otherwise we
-        // divide by inf. and return (0,0,0) vector.
-        double xx = fX;
-        double yy = fY;
-        double zz = fZ;
-#ifdef SK_CPU_FLUSH_TO_ZERO
-        // The iOS ARM processor discards small denormalized numbers to go faster.
-        // Casting this to a float would cause the scale to go to zero. Keeping it
-        // as a double for the multiply keeps the scale non-zero.
-        double dscale = 1.0f / sqrt(xx * xx + yy * yy + zz * zz);
-        fX = x * dscale;
-        fY = y * dscale;
-        fZ = z * dscale;
-        return true;
-#else
-        scale = (float)(1.0f / sqrt(xx * xx + yy * yy + zz * zz));
-#endif
-    }
-    fX *= scale;
-    fY *= scale;
-    fZ *= scale;
-    return true;
-}