Tweak the getPartitions API

- Rename methods
- Annotate public APIs with @NonNull
- implement equals/hashcode

Bug: 117146036
Bug: 112584519
Test: atest BuildVersionTest
Change-Id: I0b55e7f8e240948e674a981b280d8c8c94de6f8e
diff --git a/core/java/android/os/Build.java b/core/java/android/os/Build.java
index 8681893..a290a64 100644
--- a/core/java/android/os/Build.java
+++ b/core/java/android/os/Build.java
@@ -17,6 +17,7 @@
 package android.os;
 
 import android.Manifest;
+import android.annotation.NonNull;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
@@ -1103,19 +1104,37 @@
         }
 
         /** The name of this partition, e.g. "system", or "vendor" */
+        @NonNull
         public String getName() {
             return mName;
         }
 
         /** The build fingerprint of this partition, see {@link Build#FINGERPRINT}. */
+        @NonNull
         public String getFingerprint() {
             return mFingerprint;
         }
 
         /** The time (ms since epoch), at which this partition was built, see {@link Build#TIME}. */
-        public long getTimeMillis() {
+        public long getBuildTimeMillis() {
             return mTimeMs;
         }
+
+        @Override
+        public boolean equals(Object o) {
+            if (!(o instanceof Partition)) {
+                return false;
+            }
+            Partition op = (Partition) o;
+            return mName.equals(op.mName)
+                    && mFingerprint.equals(op.mFingerprint)
+                    && mTimeMs == op.mTimeMs;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(mName, mFingerprint, mTimeMs);
+        }
     }
 
     /**
@@ -1124,7 +1143,8 @@
      * The list includes partitions that are suitable candidates for over-the-air updates. This is
      * not an exhaustive list of partitions on the device.
      */
-    public static List<Partition> getPartitions() {
+    @NonNull
+    public static List<Partition> getFingerprintedPartitions() {
         ArrayList<Partition> partitions = new ArrayList();
 
         String[] names = new String[] {