Cleanup definition of ActivityState and ApplicationStatus warnings

Removed the redundant ActivityStateEnum intdef definition and resolved
lint warnings in the ActivityState and ApplicationStatus classes.

Also updated the c++ enum conversion doc about the new IntDef
declaration style that was added in
https://crrev.com/14f477472e0e8612c98763b68e9a51bcae954c24

BUG=707186

Review-Url: https://codereview.chromium.org/2877743002
Cr-Commit-Position: refs/heads/master@{#471432}
diff --git a/docs/android_accessing_cpp_enums_in_java.md b/docs/android_accessing_cpp_enums_in_java.md
index 4cc5fcf..fb3382e 100644
--- a/docs/android_accessing_cpp_enums_in_java.md
+++ b/docs/android_accessing_cpp_enums_in_java.md
@@ -70,15 +70,14 @@
     import java.lang.annotation.Retention;
     import java.lang.annotation.RetentionPolicy;
 
-    public class FooBar {
-      @IntDef({
-          A, B, C
-      })
-      @Retention(RetentionPolicy.SOURCE)
-      public @interface FooBarEnum {}
-      public static final int A = 0;
-      public static final int B = 1;
-      public static final int C = 1;
+    @IntDef({
+        FooBar.A, FooBar.B, FooBar.C
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface FooBar {
+      int A = 0;
+      int B = 1;
+      int C = 1;
     }
     ```
 
@@ -130,14 +129,14 @@
 
     ```java
     ...
-    public class CommentEnum {
+    public @interface CommentEnum {
       ...
       /**
        * This comment will be preserved.
        */
-      public static final int ONE = 0;
-      public static final int TWO = 1;
-      public static final int THREE = 2;
+      int ONE = 0;
+      int TWO = 1;
+      int THREE = 2;
     }
     ```