Typing fixes to eliminate casts/dcalls

tool/input_sdk/lib/collection/iterable.dart

Index: tool/input_sdk/lib/collection/iterable.dart
diff --git a/tool/input_sdk/lib/collection/iterable.dart b/tool/input_sdk/lib/collection/iterable.dart
index 154d19c2ddee9180cdcb9137cf4d3b3270d1fe7d..8020e7e68fa82012d4dc897efafc1405295f636e 100644
--- a/tool/input_sdk/lib/collection/iterable.dart
+++ b/tool/input_sdk/lib/collection/iterable.dart
@@ -120,7 +120,7 @@ abstract class IterableMixin<E> implements Iterable<E> {
   }
 
   E get first {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
@@ -128,7 +128,7 @@ abstract class IterableMixin<E> implements Iterable<E> {
   }
 
   E get last {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
@@ -140,7 +140,7 @@ abstract class IterableMixin<E> implements Iterable<E> {
   }
 
   E get single {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) throw IterableElementError.noElement();
     E result = it.current;
     if (it.moveNext()) throw IterableElementError.tooMany();
@@ -288,7 +288,7 @@ abstract class IterableBase<E> implements Iterable<E> {
   int get length {
     assert(this is! EfficientLength);
     int count = 0;
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     while (it.moveNext()) {
       count++;
     }
@@ -316,7 +316,7 @@ abstract class IterableBase<E> implements Iterable<E> {
   }
 
   E get first {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
@@ -324,7 +324,7 @@ abstract class IterableBase<E> implements Iterable<E> {
   }
 
   E get last {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) {
       throw IterableElementError.noElement();
     }
@@ -336,7 +336,7 @@ abstract class IterableBase<E> implements Iterable<E> {
   }
 
   E get single {
-    Iterator it = iterator;
+    Iterator<E> it = iterator;
     if (!it.moveNext()) throw IterableElementError.noElement();
     E result = it.current;
     if (it.moveNext()) throw IterableElementError.tooMany();