[Android] Platform check is added in browser_list.h and browser_list_observer.h

Chromium change:
https://chromium.googlesource.com/chromium/src/+/06abf006f7c6616f2b301f07dc1254639c699ecd

Add platform check in browser_list.h and browser_list_observer.h

These files are included in Android builds, but they shouldn't
be. This adds checks and fixes the include errors.

These checks are a step toward enabling gn check in chrome/browser.

Bug: 949535

browser/brave_browser_process_impl.cc

@@ -36,7 +36,9 @@
 #include "brave/services/network/public/cpp/system_request_handler.h"
 #include "chrome/browser/component_updater/component_updater_utils.h"
 #include "chrome/browser/net/system_network_context_manager.h"
+#if !defined(OS_ANDROID)
 #include "chrome/browser/ui/browser_list.h"
+#endif
 #include "chrome/common/buildflags.h"
 #include "chrome/common/chrome_paths.h"
 #include "components/component_updater/component_updater_service.h"

browser/brave_rewards/rewards_tab_helper.h

@@ -11,7 +11,9 @@
 #include "base/macros.h"
 #include "brave/components/brave_rewards/browser/rewards_service_observer.h"
 #include "build/build_config.h"
+#if !defined(OS_ANDROID)
 #include "chrome/browser/ui/browser_list_observer.h"
+#endif
 #include "components/sessions/core/session_id.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
@@ -24,7 +26,9 @@ class RewardsService;
 
 class RewardsTabHelper : public RewardsServiceObserver,
                          public content::WebContentsObserver,
+#if !defined(OS_ANDROID)
                          public BrowserListObserver,
+#endif
                          public content::WebContentsUserData<RewardsTabHelper> {
  public:
   explicit RewardsTabHelper(content::WebContents*);

components/brave_ads/browser/ads_tab_helper.h

@@ -12,7 +12,9 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "build/build_config.h"
+#if !defined(OS_ANDROID)
 #include "chrome/browser/ui/browser_list_observer.h"
+#endif
 #include "components/sessions/core/session_id.h"
 #include "content/public/browser/media_player_id.h"
 #include "content/public/browser/web_contents_observer.h"