Remove deprecated StringBuffer.add, addAll and addCharCode.

utils/template/htmltree.dart

Index: utils/template/htmltree.dart
diff --git a/utils/template/htmltree.dart b/utils/template/htmltree.dart
index 16db0a9f22ebcff6b9b29851ebd014a569dead0d..0b642c6644b21f38ac59ca977c2f9cc203b899c1 100644
--- a/utils/template/htmltree.dart
+++ b/utils/template/htmltree.dart
@@ -63,13 +63,13 @@ class TemplateSignature extends ASTNode {
     bool first = true;
     for (final param in params) {
       if (!first) {
-        buff.add(", ");
+        buff.write(", ");
       }
       if (param['type'] != null) {
-        buff.add(param['type']);
-        buff.add(' ');
+        buff.write(param['type']);
+        buff.write(' ');
       }
-      buff.add(param['name']);
+      buff.write(param['name']);
       first = false;
     }
 
@@ -102,7 +102,7 @@ class TemplateChildren extends ASTNode {
     StringBuffer buff = new StringBuffer();
     if (children != null) {
       for (final child in children) {
-        buff.add(child.toString());
+        buff.write(child.toString());
       }
     }
 
@@ -125,13 +125,13 @@ class TemplateGetter extends ASTNode {
     bool first = true;
     for (final param in params) {
       if (!first) {
-        buff.add(", ");
+        buff.write(", ");
       }
       if (param['type'] != null && param['type'].length > 0) {
-        buff.add(param['type']);
-        buff.add(' ');
+        buff.write(param['type']);
+        buff.write(' ');
       }
-      buff.add(param['name']);
+      buff.write(param['name']);
       first = false;
     }
 
@@ -182,7 +182,7 @@ class TemplateElement extends TemplateChildren {
 
     if (attributes != null) {
       for (final attr in attributes) {
-        buff.add(' ${attr.toString()}');
+        buff.write(' ${attr.toString()}');
       }
     }
 
@@ -203,10 +203,10 @@ class TemplateElement extends TemplateChildren {
 
     if (children != null) {
       for (final child in children) {
-        buff.add(child.toString());
+        buff.write(child.toString());
       }
 
-      buff.add(tagEndToString());
+      buff.write(tagEndToString());
     }
 
     return buff.toString();