Code Review Changes.

Author: dellis1972

src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Link.cs

@@ -304,7 +304,8 @@ string ExpandString (string s)
 
 		bool ExecuteForAbi (string [] cmd, string currentResourceOutputFile)
 		{
-			apks.Add (currentResourceOutputFile, RunAapt (cmd, currentResourceOutputFile));
+			lock (apks)
+				apks.Add (currentResourceOutputFile, RunAapt (cmd, currentResourceOutputFile));
 			return true;
 		}
 

src/Xamarin.Android.Build.Tasks/Tasks/ConvertCustomView.cs

@@ -79,7 +79,7 @@ public override bool RunTask ()
 					}
 				}
 			}
-			var output = new Dictionary<string, ITaskItem> ();
+			var output = new Dictionary<string, ITaskItem> (processed.Count);
 			foreach (var file in processed) {
 				ITaskItem resdir = ResourceDirectories?.FirstOrDefault (x => file.StartsWith (x.ItemSpec)) ?? null;
 				if (output.ContainsKey (file))

src/Xamarin.Android.Build.Tasks/Tasks/CopyIfChanged.cs

@@ -24,7 +24,7 @@ public class CopyIfChanged : AndroidTask
 		[Required]
 		public ITaskItem[] DestinationFiles { get; set; }
 
-		public bool CompareFileLengths { get; set; }
+		public bool CompareFileLengths { get; set; } = true;
 
 		[Output]
 		public ITaskItem[] ModifiedFiles { get; set; }
@@ -33,7 +33,6 @@ public class CopyIfChanged : AndroidTask
 
 		public CopyIfChanged ()
 		{
-			CompareFileLengths = true;
 		}
 
 		public override bool RunTask ()