Small cleanups in OTI.

- Inline a method with a misleading name.
- Remove an unused return value from a method.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=187649153

src/com/google/javascript/jscomp/TypeInference.java

@@ -435,7 +435,12 @@ private FlowScope traverse(Node n, FlowScope scope) {
       case EXPR_RESULT:
         scope = traverseChildren(n, scope);
         if (n.getFirstChild().isGetProp()) {
-          ensurePropertyDeclared(n.getFirstChild());
+          Node getprop = n.getFirstChild();
+          ObjectType ownerType = ObjectType.cast(
+              getJSType(getprop.getFirstChild()).restrictByNotNullOrUndefined());
+          if (ownerType != null) {
+            ensurePropertyDeclaredHelper(getprop, ownerType);
+          }
         }
         break;
 
@@ -724,21 +729,6 @@ private void ensurePropertyDefined(Node getprop, JSType rightType) {
     }
   }
 
-  /**
-   * Defines a declared property if it has not been defined yet.
-   *
-   * This handles the case where a property is declared on an object where
-   * the object type is inferred, and so the object type will not
-   * be known in {@code TypedScopeCreator}.
-   */
-  private void ensurePropertyDeclared(Node getprop) {
-    ObjectType ownerType = ObjectType.cast(
-        getJSType(getprop.getFirstChild()).restrictByNotNullOrUndefined());
-    if (ownerType != null) {
-      ensurePropertyDeclaredHelper(getprop, ownerType);
-    }
-  }
-
   /**
    * Declares a property on its owner, if necessary.
    * @return True if a property was declared.

src/com/google/javascript/rhino/jstype/JSTypeRegistry.java

@@ -1673,21 +1673,16 @@ public ObjectType createAnonymousObjectType(JSDocInfo info) {
 
   /**
    * Set the implicit prototype if it's possible to do so.
-   * @return True if we were able to set the implicit prototype successfully,
-   *     false if it was not possible to do so for some reason. There are
-   *     a few different reasons why this could fail: for example, numbers
-   *     can't be implicit prototypes, and we don't want to change the implicit
-   *     prototype if other classes have already subclassed this one.
-   */
-  public boolean resetImplicitPrototype(
-      JSType type, ObjectType newImplicitProto) {
+   * There are a few different reasons why this could be a no-op: for example,
+   * numbers can't be implicit prototypes, and we don't want to change the implicit prototype
+   * if other classes have already subclassed this one.
+   */
+  public void resetImplicitPrototype(JSType type, ObjectType newImplicitProto) {
     if (type instanceof PrototypeObjectType) {
       PrototypeObjectType poType = (PrototypeObjectType) type;
       poType.clearCachedValues();
       poType.setImplicitPrototype(newImplicitProto);
-      return true;
     }
-    return false;
   }
 
   /**