Initialize |bytes_so_far| local variable in SaveFileManager::SaveFinished.

content/browser/download/save_file_manager.cc

Index: content/browser/download/save_file_manager.cc
diff --git a/content/browser/download/save_file_manager.cc b/content/browser/download/save_file_manager.cc
index 0c7130e51c9e7645128323d0a32d0ee937c3cf7f..3d8940818734fda896d7c6099f6fc7424ef75b94 100644
--- a/content/browser/download/save_file_manager.cc
+++ b/content/browser/download/save_file_manager.cc
@@ -206,7 +206,7 @@ void SaveFileManager::SaveFinished(SaveItemId save_item_id,
             << " is_success = " << is_success;
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
 
-  int64_t bytes_so_far;
+  int64_t bytes_so_far = 0;

[Łukasz Anforowicz, 2016/03/24 18:23:28]

I think 0 is safe fallback here.  Initializing to some non-sensical value (like
-1 or int64-max-value) risks mishandling of the non-sense somewhere down the
code (i.e. in functions receiving this value).

PS. Before I was aware that the style guide mandates initialization everywhere,
I thought that not initializing might be preferable, because 1) the compiler can
catch it in simple cases [1] and 2) asan should catch it in more complex cases
(and after this CL this won't longer be true - the variable will always be
initialized to a "fallback" value).  Do you think this makes sense?  Does it
need a broader discussion (i.e. on chromium-dev) or is it not really worth it?

[Randy Smith (Not in Mondays), 2016/03/24 19:17:49]

I don't think a broader discussion is worth it.  This seems like a reasonable
default; I'm a bit inclined to skip the re-assignment below, and just implement
the semantic decision of "We got zero bytes unless the save file told us we got
more than zero."  

[Łukasz Anforowicz, 2016/03/24 19:25:58]

Makes sense - done.

   SaveFile* save_file = LookupSaveFile(save_item_id);
   if (save_file != nullptr) {
     DCHECK(save_file->InProgress());