Update Metadata docs and comments.

Bug: 1485768
Change-Id: Id4a4488adf10de728d0278bb66dbd617e038e6c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5278430
Reviewed-by: David Yeung <dayeung@chromium.org>
Auto-Submit: Allen Bauer <kylixrd@chromium.org>
Commit-Queue: David Yeung <dayeung@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1258052}

docs/ui/views/metadata_properties.md

@@ -22,7 +22,7 @@ In the header it is declared thusly:
 ```
 class ASH_EXPORT MyViewClass : public views::View {
  public:
-  METADATA_HEADER(MyViewClass);
+  METADATA_HEADER(MyViewClass, views::View);
 
   // ... Public API goes here ...
 
@@ -39,7 +39,7 @@ Then in the .cc file:
 ```
 class MyViewClass::MyNestedView : public views::View {
  public:
-  METADATA_HEADER(MyNestedView);
+  METADATA_HEADER(MyNestedView, views::View);
 
  // ... Public API goes here …
 

ui/views/view.h

@@ -255,16 +255,17 @@ enum class ViewLayer {
 //
 //   For Views that expose properties which are intended to be dynamically
 //   discoverable by other subsystems, each View and its descendants must
-//   include metadata. These other subsystems, such as dev tools or a delarative
-//   layout system, can then enumerate the properties on any given instance or
-//   class. Using the enumerated information, the actual values of the
-//   properties can be read or written. This will be done by getting and setting
-//   the values using string representations. The metadata can also be used to
-//   instantiate and initialize a View (or descendant) class from a declarative
-//   "script".
+//   include metadata. These other subsystems, such as dev tools or a
+//   declarative layout system, can then enumerate the properties on any given
+//   instance or class. Using the enumerated information, the actual values of
+//   the properties can be read or written. This will be done by getting and
+//   setting the values using string representations. The metadata can also be
+//   used to instantiate and initialize a View (or descendant) class from a
+//   declarative "script".
 //
 //   For each View class in their respective header declaration, place the macro
-//   METADATA_HEADER(<classname>, <view ancestor class>) in the public section.
+//   METADATA_HEADER(<classname>, <view ancestor class>) in the initial private
+//   section.
 //
 //   In the implementing .cc file, add the following macros to the same
 //   namespace in which the class resides.