Clean up error codes returned by download manager.

This set of changes cleans up the error codes returned by the download
manager in various failure cases, aiming for improved consistency.
Error codes are part of the public API so it's important to get this
right now.

The main changes here are:
* Refactoring the flow of error status information throughout
  DownloadThread to make it more explicit, by having StopRequest
  accept a status code in its constructor and eliminating
  State.mFinaStatus.
* Eliminating the use of valid HTTP 4xx statuses when those statuses
  weren't actually returned by the server.  Now, if the returned error
  code is a valid HTTP status code, that means it was returned by the
  server.  These cases have been replaced with more sensible
  artificial error codes, including a new ERROR_CANNOT_RESUME when an
  interrupted download can't be resumed.
* Improvements to some of the error handling code paths -- ensuring we
  don't clear the cache for external downloads, ensuring we don't fail
  with CANNOT_RESUME when the download hasn't actually started yet,
  removing the restriction on acceptable mime types for public API
  downloads.

Change-Id: I0d825845fe0fe7ed5df74bad26e8d34ac0d1cc4e

1 files changed, 9 insertions, 3 deletions

diff --git a/src/com/android/providers/downloads/Helpers.java b/src/com/android/providers/downloads/Helpers.java
index f2988954..5d546ff6 100644
--- a/src/com/android/providers/downloads/Helpers.java
+++ b/src/com/android/providers/downloads/Helpers.java
@@ -94,9 +94,10 @@ public class Helpers {
             String contentLocation,
             String mimeType,
             int destination,
-            long contentLength) throws FileNotFoundException {
+            long contentLength,
+            boolean isPublicApi) throws FileNotFoundException {
 
-        if (!canHandleDownload(context, mimeType, destination)) {
+        if (!canHandleDownload(context, mimeType, destination, isPublicApi)) {
             return new DownloadFileInfo(null, null, Downloads.Impl.STATUS_NOT_ACCEPTABLE);
         }
 
@@ -156,7 +157,12 @@ public class Helpers {
         return chooseUniqueFilename(destination, filename, extension, recoveryDir);
     }
 
-    private static boolean canHandleDownload(Context context, String mimeType, int destination) {
+    private static boolean canHandleDownload(Context context, String mimeType, int destination,
+            boolean isPublicApi) {
+        if (isPublicApi) {
+            return true;
+        }
+
         if (destination == Downloads.Impl.DESTINATION_EXTERNAL
                 || destination == Downloads.Impl.DESTINATION_CACHE_PARTITION_PURGEABLE) {
             if (mimeType == null) {