Android: Fix chroma sampling bug when converting from texture to YUV

webrtc/api/java/android/org/webrtc/SurfaceTextureHelper.java

Index: webrtc/api/java/android/org/webrtc/SurfaceTextureHelper.java
diff --git a/webrtc/api/java/android/org/webrtc/SurfaceTextureHelper.java b/webrtc/api/java/android/org/webrtc/SurfaceTextureHelper.java
index 4d75d6891d698739b0c90770e700b3e17034f622..5a54e904ad5062e7a699174fcefba1b4a04e86f0 100644
--- a/webrtc/api/java/android/org/webrtc/SurfaceTextureHelper.java
+++ b/webrtc/api/java/android/org/webrtc/SurfaceTextureHelper.java
@@ -251,10 +251,10 @@ class SurfaceTextureHelper {
 
       // Draw U
       GLES20.glViewport(0, height, uv_width, uv_height);
-      // Matrix * (1;0;0;0) / (2*width). Note that opengl uses column major order.
+      // Matrix * (1;0;0;0) / (width / 2). Note that opengl uses column major order.
       GLES20.glUniform2f(xUnitLoc,
-          transformMatrix[0] / (2.0f*width),
-          transformMatrix[1] / (2.0f*width));
+          2.0f * transformMatrix[0] / width,
+          2.0f * transformMatrix[1] / width);
       GLES20.glUniform4f(coeffsLoc, -0.169f, -0.331f, 0.499f, 0.5f);
       GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);