Fixed UTF8 string conversion in SimpleBrowser for Linux

- Removed "cmem" and "interfaces" from the TinyBrowser2 demo for Linux.
- Simplified the code of the TinyBrowser2 demo for Linux.
- Added the workaround for the CEF focus issue to TChromiumWindow in Linux.
- Set the result type of GetChildWindowHandle to LclType.THandle in FPC for TCEFWinControl, TCEFLinkedWindowParent and TChromiumWindow.

demos/Lazarus_Linux/SimpleBrowser/usimplebrowser.lfm

@@ -13,18 +13,18 @@ object Form1: TForm1
   LCLVersion = '2.0.10.0'
   object AddressPnl: TPanel
     Left = 0
-    Height = 21
+    Height = 25
     Top = 0
     Width = 1013
     Align = alTop
     BevelOuter = bvNone
-    ClientHeight = 21
+    ClientHeight = 25
     ClientWidth = 1013
     Enabled = False
     TabOrder = 0
     object AddressEdt: TEdit
       Left = 0
-      Height = 21
+      Height = 25
       Top = 0
       Width = 982
       Align = alClient
@@ -33,7 +33,7 @@ object Form1: TForm1
     end
     object GoBtn: TButton
       Left = 982
-      Height = 21
+      Height = 25
       Top = 0
       Width = 31
       Align = alRight
@@ -44,10 +44,11 @@ object Form1: TForm1
   end
   object ChromiumWindow1: TChromiumWindow
     Left = 0
-    Height = 684
-    Top = 21
+    Height = 680
+    Top = 25
     Width = 1013
     Align = alClient
+    TabStop = True
     TabOrder = 1
     OnBeforeClose = ChromiumWindow1BeforeClose
     OnAfterCreated = ChromiumWindow1AfterCreated

demos/Lazarus_Linux/SimpleBrowser/usimplebrowser.pas

@@ -64,7 +64,7 @@ type
     procedure FormCreate(Sender: TObject);
 
     procedure ChromiumWindow1AfterCreated(Sender: TObject);
-    procedure ChromiumWindow1BeforeClose(Sender: TObject);
+    procedure ChromiumWindow1BeforeClose(Sender: TObject);     
   private
 
   protected
@@ -136,7 +136,7 @@ begin
   FClosing  := False;
 
   // The browser will load the URL in AddressEdt initially.
-  ChromiumWindow1.ChromiumBrowser.DefaultURL := AddressEdt.Text;
+  ChromiumWindow1.ChromiumBrowser.DefaultURL := UTF8Decode(AddressEdt.Text);
 end;
 
 procedure TForm1.Chromium_OnBeforePopup(Sender: TObject;
@@ -160,7 +160,7 @@ end;
 procedure TForm1.GoBtnClick(Sender: TObject);
 begin
   // This will load the URL in the edit box
-  ChromiumWindow1.LoadURL(AddressEdt.Text);
+  ChromiumWindow1.LoadURL(UTF8Decode(AddressEdt.Text));
 end;
 
 procedure TForm1.FormActivate(Sender: TObject);