Android: Prepare moving EglBase10/EglBase14 from to API to src

BUG=webrtc:7172

Review-Url: https://codereview.webrtc.org/2826063002
Cr-Commit-Position: refs/heads/master@{#17807}

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

@@ -80,8 +80,11 @@ public abstract class EglBase {
   };
   // clang-format on
 
-  // Create a new context with the specified config attributes, sharing data with sharedContext.
+  /**
-  // |sharedContext| can be null.
+   * Create a new context with the specified config attributes, sharing data with |sharedContext|.
+   * If |sharedContext| is null, a root context is created. This function will try to create an EGL
+   * 1.4 context if possible, and an EGL 1.0 context otherwise.
+   */
   public static EglBase create(Context sharedContext, int[] configAttributes) {
     return (EglBase14.isEGL14Supported()
                && (sharedContext == null || sharedContext instanceof EglBase14.Context))
@@ -89,14 +92,36 @@ public abstract class EglBase {
         : new EglBase10((EglBase10.Context) sharedContext, configAttributes);
   }
 
+  /**
+   * Helper function for creating a plain root context. This function will try to create an EGL 1.4
+   * context if possible, and an EGL 1.0 context otherwise.
+   */
   public static EglBase create() {
-    return create(null, CONFIG_PLAIN);
+    return create(null /* shaderContext */, CONFIG_PLAIN);
   }
 
+  /**
+   * Helper function for creating a plain context, sharing data with |sharedContext|. This function
+   * will try to create an EGL 1.4 context if possible, and an EGL 1.0 context otherwise.
+   */
   public static EglBase create(Context sharedContext) {
     return create(sharedContext, CONFIG_PLAIN);
   }
 
+  /**
+   * Explicitly create a root EGl 1.0 context with the specified config attributes.
+   */
+  public static EglBase createEgl10(int[] configAttributes) {
+    return new EglBase10(null /* shaderContext */, configAttributes);
+  }
+
+  /**
+   * Explicitly create a root EGl 1.4 context with the specified config attributes.
+   */
+  public static EglBase createEgl14(int[] configAttributes) {
+    return new EglBase14(null /* shaderContext */, configAttributes);
+  }
+
   public abstract void createSurface(Surface surface);
 
   // Create EGLSurface from the Android SurfaceTexture.

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

@@ -186,7 +186,7 @@ public class EglRenderer implements VideoRenderer.Callbacks {
           // caused trouble on some weird devices.
           if (sharedContext == null) {
             logD("EglBase10.create context");
-            eglBase = new EglBase10(null /* sharedContext */, configAttributes);
+            eglBase = EglBase.createEgl10(configAttributes);
           } else {
             logD("EglBase.create shared context");
             eglBase = EglBase.create(sharedContext, configAttributes);