Document methods that are only supported on a specific Android version.

R=phensman@webrtc.org

Bug: webrtc:9819
Change-Id: Ifd3da9e1b70d0cfc479777c3a8031f632296be38
Reviewed-on: https://webrtc-review.googlesource.com/c/103680
Reviewed-by: Paulina Hensman <phensman@webrtc.org>
Commit-Queue: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24987}

sdk/android/api/org/webrtc/EglBase.java

@@ -11,8 +11,8 @@
 package org.webrtc;
 
 import android.graphics.SurfaceTexture;
-import javax.annotation.Nullable;
 import android.view.Surface;
+import javax.annotation.Nullable;
 import javax.microedition.khronos.egl.EGL10;
 
 /**
@@ -21,7 +21,15 @@ import javax.microedition.khronos.egl.EGL10;
  */
 public interface EglBase {
   // EGL wrapper for an actual EGLContext.
-  public interface Context { long getNativeEglContext(); }
+  public interface Context {
+    /**
+     * Returns an EGL context that can be used by native code. Returns 0 if the method is
+     * unsupported.
+     *
+     * @note This is currently only supported for EGL 1.4 and not for EGL 1.0.
+     */
+    long getNativeEglContext();
+  }
 
   // According to the documentation, EGL can be used from multiple threads at the same time if each
   // thread has its own EGLContext, but in practice it deadlocks on some devices when doing this.

sdk/android/api/org/webrtc/ScreenCapturerAndroid.java

@@ -31,6 +31,8 @@ import javax.annotation.Nullable;
  * place on the HandlerThread of the given {@code SurfaceTextureHelper}. When done with each frame,
  * the native code returns the buffer to the  {@code SurfaceTextureHelper} to be used for new
  * frames. At any time, at most one frame is being processed.
+ *
+ * @note This class is only supported on Android Lollipop and above.
  */
 @TargetApi(21)
 public class ScreenCapturerAndroid implements VideoCapturer, VideoSink {