mojo: java core API: Allow interaction with native handles

This adds API to convert handle to and from int to allow interaction
with native code.

R=ppi@chromium.org

Review URL: https://codereview.chromium.org/544103002

Cr-Commit-Position: refs/heads/master@{#293703}

mojo/android/javatests/src/org/chromium/mojo/HandleMock.java

@@ -73,6 +73,14 @@ public class HandleMock implements UntypedHandle, MessagePipeHandle,
         return this;
     }
 
+    /**
+     * @see Handle#releaseNativeHandle()
+     */
+    @Override
+    public int releaseNativeHandle() {
+        return 0;
+    }
+
     /**
      * @see ConsumerHandle#discardData(int, DataPipe.ReadFlags)
      */

mojo/android/javatests/src/org/chromium/mojo/system/impl/CoreImplTest.java

@@ -817,4 +817,22 @@ public class CoreImplTest extends MojoTestCase {
         checkSharing(newHandleClone, handleClone);
     }
 
+    /**
+     * esting handle conversion to native and back.
+     */
+    @SmallTest
+    public void testHandleConversion() {
+        Core core = CoreImpl.getInstance();
+        Pair<MessagePipeHandle, MessagePipeHandle> handles = core.createMessagePipe(null);
+        addHandlePairToClose(handles);
+
+        MessagePipeHandle converted =
+                core.acquireNativeHandle(handles.first.releaseNativeHandle()).toMessagePipeHandle();
+        addHandleToClose(converted);
+
+        assertFalse(handles.first.isValid());
+
+        checkSendingMessage(converted, handles.second);
+        checkSendingMessage(handles.second, converted);
+    }
 }

mojo/android/system/src/org/chromium/mojo/system/impl/CoreImpl.java

@@ -170,6 +170,14 @@ public class CoreImpl implements Core, AsyncWaiter {
         return new SharedBufferHandleImpl(this, result.getMojoHandle1());
     }
 
+    /**
+     * @see org.chromium.mojo.system.Core#acquireNativeHandle(int)
+     */
+    @Override
+    public UntypedHandle acquireNativeHandle(int handle) {
+        return new UntypedHandleImpl(this, handle);
+    }
+
     /**
      * @see Core#getDefaultAsyncWaiter()
      */

mojo/android/system/src/org/chromium/mojo/system/impl/HandleBase.java

@@ -93,6 +93,16 @@ abstract class HandleBase implements Handle {
         return mCore;
     }
 
+    /**
+     * @see Handle#releaseNativeHandle()
+     */
+    @Override
+    public int releaseNativeHandle() {
+        int result = mMojoHandle;
+        mMojoHandle = CoreImpl.INVALID_HANDLE;
+        return result;
+    }
+
     /**
      * Getter for the native scoped handle.
      *

mojo/public/java/system/src/org/chromium/mojo/system/Core.java

@@ -179,6 +179,14 @@ public interface Core {
     public SharedBufferHandle createSharedBuffer(SharedBufferHandle.CreateOptions options,
             long numBytes);
 
+    /**
+     * Acquires a handle from the native side. The handle will be owned by the returned object and
+     * must not be closed outside of it.
+     *
+     * @return a new {@link UntypedHandle} representing the native handle.
+     */
+    public UntypedHandle acquireNativeHandle(int handle);
+
     /**
      * Returns a default implementation of {@link AsyncWaiter}.
      */

mojo/public/java/system/src/org/chromium/mojo/system/Handle.java

@@ -50,4 +50,10 @@ public interface Handle extends Closeable {
      */
     public Handle pass();
 
+    /**
+     * Releases the native handle backed by this {@link Handle}. The caller owns the handle and must
+     * close it.
+     */
+    public int releaseNativeHandle();
+
 }

mojo/public/java/system/src/org/chromium/mojo/system/InvalidHandle.java

@@ -68,7 +68,6 @@ public class InvalidHandle implements UntypedHandle, MessagePipeHandle, Consumer
         return this;
     }
 
-
     /**
      * @see Handle#toUntypedHandle()
      */
@@ -77,6 +76,14 @@ public class InvalidHandle implements UntypedHandle, MessagePipeHandle, Consumer
         return this;
     }
 
+    /**
+     * @see Handle#releaseNativeHandle()
+     */
+    @Override
+    public int releaseNativeHandle() {
+        return -1;
+    }
+
     /**
      * @see UntypedHandle#toMessagePipeHandle()
      */