Add @HalfFloat annotation for fp16 data types stored in shorts

This CL has a companion CL to add the @HalfFloat annotation to the
support library.

Test: cts-tradefed run singleCommand cts-dev --module CtsUtilTestCases --test android.util.cts.HalfTest
Bug: 29940137
Change-Id: I4e1dc456687c1c026437150e9cc94a54f3264d4e
diff --git a/java/android/annotation/HalfFloat.java b/java/android/annotation/HalfFloat.java
new file mode 100644
index 0000000..d3e9f08
--- /dev/null
+++ b/java/android/annotation/HalfFloat.java
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.annotation;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+import static java.lang.annotation.ElementType.FIELD;
+import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PARAMETER;
+import static java.lang.annotation.RetentionPolicy.SOURCE;
+
+/**
+ * <p>Denotes that the annotated element represents a half-precision floating point
+ * value. Such values are stored in short data types and can be manipulated with
+ * the {@link android.util.Half} class. If applied to an array of short, every
+ * element in the array represents a half-precision float.</p>
+ *
+ * <p>Example:</p>
+ *
+ * <pre>{@code
+ * public abstract void setPosition(@HalfFloat short x, @HalfFloat short y, @HalfFloat short z);
+ * }</pre>
+ *
+ * @see android.util.Half
+ * @see android.util.Half#valueOf(float)
+ * @see android.util.Half#toFloat(short)
+ *
+ * @hide
+ */
+@Retention(SOURCE)
+@Target({PARAMETER, METHOD, LOCAL_VARIABLE, FIELD})
+public @interface HalfFloat {
+}