make sqlite storage more resilient to sporadic errors

- catch SQLite exceptions and report them
- failed statements are ignored, we're really just caching here, so if it fails we're handling it gracefully elsewhere
- handle cases where the database file goes away after we opened it
- handle cases where the schema wasn't created after the database file was opened successfully
- add tests

1 files changed, 6 insertions, 0 deletions

diff --git a/src/mbgl/platform/log.cpp b/src/mbgl/platform/log.cpp
index d6cbc4fd11..2a761c6260 100644
--- a/src/mbgl/platform/log.cpp
+++ b/src/mbgl/platform/log.cpp
@@ -17,6 +17,12 @@ void Log::setObserver(std::unique_ptr<Observer> observer) {
     currentObserver = std::move(observer);
 }
 
+std::unique_ptr<Log::Observer> Log::removeObserver() {
+    std::unique_ptr<Observer> observer;
+    std::swap(observer, currentObserver);
+    return observer;
+}
+
 void Log::record(EventSeverity severity, Event event, const std::string &msg) {
     record(severity, event, -1, msg);
 }