Add documents for isOem/Vendor/Product

Bug: 182793544
Bug: 182285645
Test: m
Change-Id: I3b0353c38f74143e40540617fbaf2e247f152918
diff --git a/core/java/android/content/pm/ApplicationInfo.java b/core/java/android/content/pm/ApplicationInfo.java
index 6ec1169..ad9e31b 100644
--- a/core/java/android/content/pm/ApplicationInfo.java
+++ b/core/java/android/content/pm/ApplicationInfo.java
@@ -2167,7 +2167,10 @@
         return (flags & ApplicationInfo.FLAG_EXTERNAL_STORAGE) == 0;
     }
 
-    /** @hide */
+    /**
+     * True if the application is pre-installed on the OEM partition of the system image.
+     * @hide
+     */
     @SystemApi
     public boolean isOem() {
         return (privateFlags & ApplicationInfo.PRIVATE_FLAG_OEM) != 0;
@@ -2215,13 +2218,19 @@
         return (flags & ApplicationInfo.FLAG_UPDATED_SYSTEM_APP) != 0;
     }
 
-    /** @hide */
+    /**
+     * True if the application is pre-installed on the vendor partition of the system image.
+     * @hide
+     */
     @SystemApi
     public boolean isVendor() {
         return (privateFlags & ApplicationInfo.PRIVATE_FLAG_VENDOR) != 0;
     }
 
-    /** @hide */
+    /**
+     * True if the application is pre-installed on the product partition of the system image.
+     * @hide
+     */
     @SystemApi
     public boolean isProduct() {
         return (privateFlags & ApplicationInfo.PRIVATE_FLAG_PRODUCT) != 0;