Remove third_party/golang.org/x/mobile as it is no longer used with Go 1.5.

third_party/go/src/golang.org/x/mobile/f32/mat3.go

-// Copyright 2014 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package f32
-
-import "fmt"
-
-// A Mat3 is a 3x3 matrix of float32 values.
-// Elements are indexed first by row then column, i.e. m[row][column].
-type Mat3 [3]Vec3
-
-func (m Mat3) String() string {
-        return fmt.Sprintf(`Mat3[% 0.3f, % 0.3f, % 0.3f,
-     % 0.3f, % 0.3f, % 0.3f,
-     % 0.3f, % 0.3f, % 0.3f]`,
-                m[0][0], m[0][1], m[0][2],
-                m[1][0], m[1][1], m[1][2],
-                m[2][0], m[2][1], m[2][2])
-}
-
-func (m *Mat3) Identity() {
-        *m = Mat3{
-                {1, 0, 0},
-                {0, 1, 0},
-                {0, 0, 1},
-        }
-}
-
-func (m *Mat3) Eq(n *Mat3, epsilon float32) bool {
-        for i := range m {
-                for j := range m[i] {
-                        diff := m[i][j] - n[i][j]
-                        if diff < -epsilon || +epsilon < diff {
-                                return false
-                        }
-                }
-        }
-        return true
-}
-
-// Mul stores a × b in m.
-func (m *Mat3) Mul(a, b *Mat3) {
-        // Store the result in local variables, in case m == a || m == b.
-        m00 := a[0][0]*b[0][0] + a[0][1]*b[1][0] + a[0][2]*b[2][0]
-        m01 := a[0][0]*b[0][1] + a[0][1]*b[1][1] + a[0][2]*b[2][1]
-        m02 := a[0][0]*b[0][2] + a[0][1]*b[1][2] + a[0][2]*b[2][2]
-        m10 := a[1][0]*b[0][0] + a[1][1]*b[1][0] + a[1][2]*b[2][0]
-        m11 := a[1][0]*b[0][1] + a[1][1]*b[1][1] + a[1][2]*b[2][1]
-        m12 := a[1][0]*b[0][2] + a[1][1]*b[1][2] + a[1][2]*b[2][2]
-        m20 := a[2][0]*b[0][0] + a[2][1]*b[1][0] + a[2][2]*b[2][0]
-        m21 := a[2][0]*b[0][1] + a[2][1]*b[1][1] + a[2][2]*b[2][1]
-        m22 := a[2][0]*b[0][2] + a[2][1]*b[1][2] + a[2][2]*b[2][2]
-        m[0][0] = m00
-        m[0][1] = m01
-        m[0][2] = m02
-        m[1][0] = m10
-        m[1][1] = m11
-        m[1][2] = m12
-        m[2][0] = m20
-        m[2][1] = m21
-        m[2][2] = m22
-}