[Cronet] Separate Cronet implementation and API by package name.

components/cronet/android/api/src/org/chromium/net/Preconditions.java

Index: components/cronet/android/api/src/org/chromium/net/Preconditions.java
diff --git a/components/cronet/android/api/src/org/chromium/net/Preconditions.java b/components/cronet/android/api/src/org/chromium/net/Preconditions.java
index babce3745ec1f61ef89331a4fc5eff5822a8a345..4abe9612bb8253700a3044dd97335b931a7843ca 100644
--- a/components/cronet/android/api/src/org/chromium/net/Preconditions.java
+++ b/components/cronet/android/api/src/org/chromium/net/Preconditions.java
@@ -6,16 +6,19 @@ package org.chromium.net;
 
 import java.nio.ByteBuffer;
 
-final class Preconditions {
+/**
+ * {@hide only used by internal implementation.}
+ */
+public final class Preconditions {
     private Preconditions() {}
 
-    static void checkDirect(ByteBuffer buffer) {
+    public static void checkDirect(ByteBuffer buffer) {
         if (!buffer.isDirect()) {
             throw new IllegalArgumentException("byteBuffer must be a direct ByteBuffer.");
         }
     }
 
-    static void checkHasRemaining(ByteBuffer buffer) {
+    public static void checkHasRemaining(ByteBuffer buffer) {
         if (!buffer.hasRemaining()) {
             throw new IllegalArgumentException("ByteBuffer is already full.");
         }