Add @SystemApi annotation to parcel.writeBlob and readBlob.

AppSearch will put text-based document via binder to server side.
Parcel.writeBlob could take care of decide where to put in Android
Shared Memory if data is too large.
Remove {@SystemApi} to make it available for AppSearch.

Bug: 185441119
Test: presubmit
Change-Id: I95218fdca2baa5b4a287f05c9d79273b4a6e622c

core/api/current.txt

@@ -31728,6 +31728,7 @@ package android.os {
     method @Nullable public <T> java.util.ArrayList<T> readArrayList(@Nullable ClassLoader, @NonNull Class<? extends T>);
     method public void readBinderArray(@NonNull android.os.IBinder[]);
     method public void readBinderList(@NonNull java.util.List<android.os.IBinder>);
+    method @Nullable public byte[] readBlob();
     method public boolean readBoolean();
     method public void readBooleanArray(@NonNull boolean[]);
     method @Nullable public android.os.Bundle readBundle();
@@ -31786,6 +31787,8 @@ package android.os {
     method public void writeArray(@Nullable Object[]);
     method public void writeBinderArray(@Nullable android.os.IBinder[]);
     method public void writeBinderList(@Nullable java.util.List<android.os.IBinder>);
+    method public void writeBlob(@Nullable byte[]);
+    method public void writeBlob(@Nullable byte[], int, int);
     method public void writeBoolean(boolean);
     method public void writeBooleanArray(@Nullable boolean[]);
     method public void writeBundle(@Nullable android.os.Bundle);

core/java/android/os/Parcel.java

@@ -902,11 +902,15 @@ public final class Parcel {
     /**
      * Write a blob of data into the parcel at the current {@link #dataPosition},
      * growing {@link #dataCapacity} if needed.
+     *
+     * <p> If the blob is small, then it is stored in-place, otherwise it is transferred by way of
+     * an anonymous shared memory region. If you prefer send in-place, please use
+     * {@link #writeByteArray(byte[])}.
+     *
      * @param b Bytes to place into the parcel.
-     * {@hide}
-     * {@SystemApi}
+     *
+     * @see #readBlob()
      */
-    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
     public final void writeBlob(@Nullable byte[] b) {
         writeBlob(b, 0, (b != null) ? b.length : 0);
     }
@@ -914,11 +918,16 @@ public final class Parcel {
     /**
      * Write a blob of data into the parcel at the current {@link #dataPosition},
      * growing {@link #dataCapacity} if needed.
+     *
+     * <p> If the blob is small, then it is stored in-place, otherwise it is transferred by way of
+     * an anonymous shared memory region. If you prefer send in-place, please use
+     * {@link #writeByteArray(byte[], int, int)}.
+     *
      * @param b Bytes to place into the parcel.
      * @param offset Index of first byte to be written.
      * @param len Number of bytes to write.
-     * {@hide}
-     * {@SystemApi}
+     *
+     * @see #readBlob()
      */
     public final void writeBlob(@Nullable byte[] b, int offset, int len) {
         if (b == null) {
@@ -3197,10 +3206,8 @@ public final class Parcel {
 
     /**
      * Read a blob of data from the parcel and return it as a byte array.
-     * {@hide}
-     * {@SystemApi}
+     * @see #writeBlob(byte[], int, int)
      */
-    @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553)
     @Nullable
     public final byte[] readBlob() {
         return nativeReadBlob(mNativePtr);