[Mixed Content DL Blocking] Exclude known cases from dump-without-crashing.

This CL updates the cases in which mixed content download blocking will
dump without crashing by excluding now-known cases where initiators are
missing. These include downloads from webview/cct, internally-initiated
downloads and user-initiated downloads of offline pages.

It also silences dumps from a not-yet-understood situation where
seemingly-normal downloads don't have initiators. The stack trace isn't
helping in this case, so crash dumps aren't useful.

Bug: 1029003
Change-Id: I77102e361d334e847331f5e0bc1b9ce5321ab4a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1940723
Commit-Queue: Joe DeBlasio <jdeblasio@chromium.org>
Auto-Submit: Joe DeBlasio <jdeblasio@chromium.org>
Reviewed-by: Mustafa Emre Acer <meacer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719731}

chrome/browser/download/mixed_content_download_blocking.cc

@@ -22,6 +22,8 @@
 #include "url/gurl.h"
 #include "url/origin.h"
 
+using download::DownloadSource;
+
 namespace {
 
 // Map the string file extension to the corresponding histogram enum.
@@ -183,16 +185,38 @@ bool ShouldBlockFileAsMixedContent(const base::FilePath& path,
     is_inferred = true;
   }
 
-  if (is_inferred &&
-      item.GetDownloadSource() != download::DownloadSource::CONTEXT_MENU) {
+  auto download_source = item.GetDownloadSource();
+  auto transition_type = item.GetTransitionType();
+
+  // Report a trace if we inferred an initiator in an unexpected way. We expect
+  // this to happen with:
+  //  - context-menu-initiated downloads,
+  //  - user-initiated downloads of offline pages on Android,
+  //  - requests in e.g., webview/CCT.
+  //
+  // TODO(1029082): We also occasionally find 'regular' navigations without
+  // initiators (NAVIGATION/PAGE_TRANSITION_LINK).  The trace doesn't help in
+  // this case, so ignore them here.
+  if (is_inferred && download_source != DownloadSource::CONTEXT_MENU &&
+      download_source != DownloadSource::OFFLINE_PAGE &&
+      !(transition_type & ui::PAGE_TRANSITION_FROM_API) &&
+      !(download_source == DownloadSource::NAVIGATION &&
+        PageTransitionTypeIncludingQualifiersIs(transition_type,
+                                                ui::PAGE_TRANSITION_LINK))) {
     ReportTrace(base::StringPrintf("inferred initiator [%d, %x]",
-                                   item.GetDownloadSource(),
-                                   item.GetTransitionType()));
+                                   download_source, transition_type));
   }
-  if (!initiator.has_value()) {
+
+  // Report a trace if we still don't have an initiator. This mostly happens
+  // with INTERNAL_API calls, which are OK.
+  //
+  // TODO(1029062): INTERNAL_API is also used for background fetch. That
+  // probably isn't the correct behavior, since INTERNAL_API is otherwise used
+  // for Chrome stuff. Background fetch should probably be HTTPS-only.
+  if (!initiator.has_value() &&
+      download_source != DownloadSource::INTERNAL_API) {
     ReportTrace(base::StringPrintf("no initiator found [%d, %x]",
-                                   item.GetDownloadSource(),
-                                   item.GetTransitionType()));
+                                   download_source, transition_type));
   }
 
   // Then see if that extension is blocked