Fix and optimize input buffer filling in HardwareVideoEncoder.

Previously input buffers would be filled incorrectly for sparsely
packed buffers where stride is not equal to the plane width.

Bug: webrtc:8478
Change-Id: I080fa3c354a27982bb996be8c1e41b103384e4bc
Reviewed-on: https://webrtc-review.googlesource.com/17321
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20550}

sdk/android/instrumentationtests/src/org/webrtc/HardwareVideoEncoderTest.java

@@ -328,6 +328,8 @@ public class HardwareVideoEncoderTest {
   // # Tests
   @Before
   public void setUp() {
+    NativeLibrary.initialize(new NativeLibrary.DefaultLoader());
+
     eglBase = new EglBase14(null, EglBase.CONFIG_PLAIN);
     eglBase.createDummyPbufferSurface();
     eglBase.makeCurrent();