Fix green screen problem when using VpxRenderer.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=120689946

extensions/vp9/src/main/java/com/google/android/exoplayer/ext/vp9/VpxRenderer.java

@@ -78,6 +78,7 @@ import javax.microedition.khronos.opengles.GL10;
   private int program;
   private int texLocation;
   private int colorMatrixLocation;
+  private FloatBuffer textureCoords;
   private int previousWidth;
   private int previousStride;
 
@@ -170,7 +171,9 @@ import javax.microedition.khronos.opengles.GL10;
     // Set cropping of stride if either width or stride has changed.
     if (previousWidth != outputBuffer.width || previousStride != outputBuffer.yuvStrides[0]) {
       float crop = (float) outputBuffer.width / outputBuffer.yuvStrides[0];
-      FloatBuffer textureCoords = nativeFloatBuffer(
+      // This buffer is consumed during each call to glDrawArrays. It needs to be a member variable
+      // rather than a local variable to ensure that it doesn't get garbage collected.
+      textureCoords = nativeFloatBuffer(
           0.0f, 0.0f,
           0.0f, 1.0f,
           crop, 0.0f,