ui/base/clipboard: Make ClipboardFormatType a class.

It's possible this should have been a struct when it was created, but that time
is long gone. ClipboardFormatType is now fairly complex and can hold multiple
private members. Therefore, as per the Style Guide[1], this should now be a
class instead of a struct.

[1]: https://google.github.io/styleguide/cppguide.html#Structs_vs._Classes

Change-Id: I3eab2fc75d9660fbc5aa05322df7d12034d113fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2020477Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Jarryd Goodman <jarrydg@chromium.org>
Commit-Queue: Darwin Huang <huangdarwin@chromium.org>
Auto-Submit: Darwin Huang <huangdarwin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736544}

content/browser/frame_host/render_frame_host_delegate.h

@@ -73,7 +73,7 @@ class FullscreenOptions;
 }  // namespace blink
 
 namespace ui {
-struct ClipboardFormatType;
+class ClipboardFormatType;
 }
 
 namespace content {

content/browser/frame_host/render_frame_host_impl.h

@@ -168,7 +168,7 @@ class ResourceRequestBody;
 }  // namespace network
 
 namespace ui {
-struct ClipboardFormatType;
+class ClipboardFormatType;
 }
 
 namespace content {

content/public/browser/content_browser_client.h

@@ -158,7 +158,7 @@ class TargetPolicy;
 
 namespace ui {
 class SelectFilePolicy;
-struct ClipboardFormatType;
+class ClipboardFormatType;
 }  // namespace ui
 
 namespace url {

ui/base/clipboard/clipboard_format_type.h

@@ -29,7 +29,8 @@ namespace ui {
 
 // Platform neutral holder for native data representation of a clipboard type.
 // Copyable and assignable, since this is an opaque value type.
-struct COMPONENT_EXPORT(UI_BASE_CLIPBOARD_TYPES) ClipboardFormatType {
+class COMPONENT_EXPORT(UI_BASE_CLIPBOARD_TYPES) ClipboardFormatType {
+ public:
   ClipboardFormatType();
   ~ClipboardFormatType();
 
@@ -105,7 +106,6 @@ struct COMPONENT_EXPORT(UI_BASE_CLIPBOARD_TYPES) ClipboardFormatType {
  private:
   friend class base::NoDestructor<ClipboardFormatType>;
   friend class Clipboard;
-  friend struct ClipboardFormatType;
 
   // Platform-specific glue used internally by the ClipboardFormatType struct.
   // Each platform should define at least one of each of the following:

ui/base/dragdrop/os_exchange_data.h

@@ -35,7 +35,7 @@ class Vector2d;
 
 namespace ui {
 
-struct ClipboardFormatType;
+class ClipboardFormatType;
 struct FileInfo;
 
 ///////////////////////////////////////////////////////////////////////////////

ui/base/dragdrop/os_exchange_data_provider_aura.h

@@ -17,7 +17,7 @@
 
 namespace ui {
 
-struct ClipboardFormatType;
+class ClipboardFormatType;
 
 // OSExchangeData::Provider implementation for aura on linux.
 class UI_BASE_EXPORT OSExchangeDataProviderAura