Revert "AIR-9: Do not cancel stackwalk when module not found."

This reverts commit 8b84378.

src/processor/stack_frame_symbolizer.cc

@@ -79,9 +79,7 @@ StackFrameSymbolizer::SymbolizerResult StackFrameSymbolizer::FillSourceLineInfo(
   // If module is known to have missing symbol file, return.
   if (no_symbol_modules_.find(module->code_file()) !=
       no_symbol_modules_.end()) {
-    //BZ: Previously, this would generate an error, which would cancel
-    // the remainder of the stackwalk.
-    return kNoError;
+    return kError;
   }
 
   // If module is already loaded, go ahead to fill source line info and return.
@@ -118,11 +116,9 @@ StackFrameSymbolizer::SymbolizerResult StackFrameSymbolizer::FillSourceLineInfo(
         return resolver_->IsModuleCorrupt(frame->module) ?
             kWarningCorruptSymbols : kNoError;
       } else {
-        //BZ: Previously, this would generate an error, which would cancel
-        // the remainder of the stackwalk.
         BPLOG(ERROR) << "Failed to load symbol file in resolver.";
         no_symbol_modules_.insert(module->code_file());
-        return kNoError;
+        return kError;
       }
     }