Inspect content type from trailers when there are no headers.

-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=81291102

core/src/main/java/com/google/net/stubby/transport/Http2ClientStream.java

@@ -47,6 +47,7 @@ public abstract class Http2ClientStream extends AbstractClientStream<Integer> {
 
   private Status transportError;
   private Charset errorCharset = Charsets.UTF_8;
+  private boolean contentTypeChecked;
 
   protected Http2ClientStream(ClientStreamListener listener,
                               @Nullable Decompressor decompressor,
@@ -61,23 +62,20 @@ public abstract class Http2ClientStream extends AbstractClientStream<Integer> {
       transportError = transportError.augmentDescription(headers.toString());
       return;
     }
-    String contentType = headers.get(HttpUtil.CONTENT_TYPE);
     Status httpStatus = statusFromHttpStatus(headers);
     if (httpStatus == null) {
       transportError = Status.INTERNAL.withDescription(
           "received non-terminal headers with no :status");
     } else if (!httpStatus.isOk()) {
       transportError = httpStatus;
-    } else if (TEMP_CHECK_CONTENT_TYPE &&
+    } else {
-        !HttpUtil.CONTENT_TYPE_GRPC.equalsIgnoreCase(contentType)) {
+      transportError = checkContentType(headers);
-      // Malformed content-type so report an error
-      transportError = Status.INTERNAL.withDescription("invalid content-type " + contentType);
     }
     if (transportError != null) {
       // Note we don't immediately report the transport error, instead we wait for more data on the
       // stream so we can accumulate more detail into the error before reporting it.
       transportError = transportError.withDescription("\n" + headers.toString());
-      errorCharset = charsetFromContentType(contentType);
+      errorCharset = extractCharset(headers);
     } else {
       stripTransportDetails(headers);
       inboundHeadersReceived(headers);
@@ -137,6 +135,10 @@ public abstract class Http2ClientStream extends AbstractClientStream<Integer> {
     if (transportError != null) {
       // Already received a transport error so just augment it.
       transportError = transportError.augmentDescription(trailers.toString());
+    } else {
+      transportError = checkContentType(trailers);
+    }
+    if (transportError != null) {
       inboundTransportError(transportError);
     } else {
       Status status = statusFromTrailers(trailers);
@@ -178,10 +180,29 @@ public abstract class Http2ClientStream extends AbstractClientStream<Integer> {
     return status;
   }
 
+  /**
+   * Inspect the content type field from received headers or trailers and return an error Status if
+   * content type is invalid or not present. Returns null if no error was found.
+   */
+  @Nullable
+  private Status checkContentType(Metadata headers) {
+    if (contentTypeChecked) {
+      return null;
+    }
+    contentTypeChecked = true;
+    String contentType = headers.get(HttpUtil.CONTENT_TYPE);
+    if (TEMP_CHECK_CONTENT_TYPE && !HttpUtil.CONTENT_TYPE_GRPC.equalsIgnoreCase(contentType)) {
+      // Malformed content-type so report an error
+      return Status.INTERNAL.withDescription("invalid content-type " + contentType);
+    }
+    return null;
+  }
+
   /**
    * Inspect the raw metadata and figure out what charset is being used.
    */
-  private static Charset charsetFromContentType(String contentType) {
+  private static Charset extractCharset(Metadata headers) {
+    String contentType = headers.get(HttpUtil.CONTENT_TYPE);
     if (contentType != null) {
       String[] split = contentType.split("charset=");
       try {