DropBoxManager: Allow adding a file using an fd

This patch adds an overload to DropBoxManager::addFile() which accepts
an already-opened file as a file descriptor. This avoids the need for
clients to create a filesystem-visible file when uploading data to
DropBox.

Test: Tested with perfetto using https://android-review.googlesource.com/c/platform/external/perfetto/+/587674
Change-Id: I076bfd3180fb9b4baff7e1bae2e611419061b2a7
Merged-In: I076bfd3180fb9b4baff7e1bae2e611419061b2a7

libs/services/include/android/os/DropBoxManager.h

@@ -57,7 +57,11 @@ public:
     // and a handle will be passed to the system process, so no additional permissions
     // are required from the system process.  Returns NULL if the file can't be opened.
     Status addFile(const String16& tag, const string& filename, int flags);
-    
+
+    // Create a new Entry from an already opened file. Takes ownership of the
+    // file descriptor.
+    Status addFile(const String16& tag, int fd, int flags);
+
     class Entry : public virtual RefBase, public Parcelable {
     public:
         Entry();

libs/services/src/os/DropBoxManager.cpp

@@ -179,7 +179,12 @@ DropBoxManager::addFile(const String16& tag, const string& filename, int flags)
         ALOGW("DropboxManager: %s", message.c_str());
         return Status::fromExceptionCode(Status::EX_ILLEGAL_STATE, message.c_str());
     }
+    return addFile(tag, fd, flags);
+}
 
+Status
+DropBoxManager::addFile(const String16& tag, int fd, int flags)
+{
     Entry entry(tag, flags, fd);
     return add(entry);
 }