dart2js: Trust type annotations more often with --trust-type-annotation.

pkg/compiler/lib/src/ssa/types_propagation.dart

Index: pkg/compiler/lib/src/ssa/types_propagation.dart
diff --git a/pkg/compiler/lib/src/ssa/types_propagation.dart b/pkg/compiler/lib/src/ssa/types_propagation.dart
index eb21bb402cb70999d5514ab5e0ceea01109835e3..4f3e7eec8f94605553b1d5fb0e39d066f961fe10 100644
--- a/pkg/compiler/lib/src/ssa/types_propagation.dart
+++ b/pkg/compiler/lib/src/ssa/types_propagation.dart
@@ -183,13 +183,21 @@ class SsaTypePropagator extends HBaseVisitor implements OptimizationPhase {
         }
       }
     }
+    if (inputType != outputType) {
+      input.replaceAllUsersDominatedBy(instruction.next, instruction);
+    }
     return outputType;
   }
 
   TypeMask visitTypeKnown(HTypeKnown instruction) {
     HInstruction input = instruction.checkedInput;
-    return instruction.knownType.intersection(
-        input.instructionType, classWorld);
+    TypeMask inputType = input.instructionType;
+    TypeMask outputType =
+        instruction.knownType.intersection(inputType, classWorld);
+    if (inputType != outputType) {
+      input.replaceAllUsersDominatedBy(instruction.next, instruction);
+    }
+    return outputType;
   }
 
   void convertInput(HInvokeDynamic instruction,