Consider TextInputController::inputMethodController() could be nullptr.

components/test_runner/text_input_controller.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/test_runner/text_input_controller.h"
 
 #include "base/macros.h"
 #include "components/test_runner/web_test_delegate.h"
 #include "components/test_runner/web_view_test_proxy.h"
 #include "gin/arguments.h"
 #include "gin/handle.h"
 #include "gin/object_template_builder.h"
 #include "gin/wrappable.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
+#include "third_party/WebKit/public/platform/WebInputEventResult.h"
 #include "third_party/WebKit/public/web/WebCompositionUnderline.h"
 #include "third_party/WebKit/public/web/WebFrameWidget.h"
 #include "third_party/WebKit/public/web/WebInputMethodController.h"
 #include "third_party/WebKit/public/web/WebKit.h"
 #include "third_party/WebKit/public/web/WebLocalFrame.h"
 #include "third_party/WebKit/public/web/WebRange.h"
 #include "third_party/WebKit/public/web/WebView.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "v8/include/v8.h"
 
@@ skipping 136 matching lines @@
     : web_view_test_proxy_base_(web_view_test_proxy_base),
       weak_factory_(this) {}
 
 TextInputController::~TextInputController() {}
 
 void TextInputController::Install(blink::WebLocalFrame* frame) {
   TextInputControllerBindings::Install(weak_factory_.GetWeakPtr(), frame);
 }
 
 void TextInputController::InsertText(const std::string& text) {
-  inputMethodController()->commitText(blink::WebString::fromUTF8(text), 0);
+  if (auto* controller = GetInputMethodController()) {
+    controller->commitText(blink::WebString::fromUTF8(text), 0);
+  }
 }
 
 void TextInputController::UnmarkText() {
-  inputMethodController()->finishComposingText(
-      blink::WebInputMethodController::KeepSelection);
+  if (auto* controller = GetInputMethodController()) {
+    controller->finishComposingText(
+        blink::WebInputMethodController::KeepSelection);
+  }
 }
 
 void TextInputController::DoCommand(const std::string& text) {
   if (view()->mainFrame()) {
     if (!view()->mainFrame()->toWebLocalFrame()) {
       CHECK(false) << "This function cannot be called if the main frame is not"
                       "a local frame.";
     }
     view()->mainFrame()->toWebLocalFrame()->executeCommand(
         blink::WebString::fromUTF8(text));
@@ skipping 18 matching lines @@
   }
   underline.thick = true;
   underlines.push_back(underline);
   if (start + length < static_cast<int>(web_text.length())) {
     underline.startOffset = underline.endOffset;
     underline.endOffset = web_text.length();
     underline.thick = false;
     underlines.push_back(underline);
   }
 
-  inputMethodController()->setComposition(web_text, underlines, start,
-                                          start + length);
+  if (auto* controller = GetInputMethodController()) {
+    controller->setComposition(web_text, underlines, start, start + length);
+  }
 }
 
 bool TextInputController::HasMarkedText() {
   if (!view()->mainFrame())
     return false;
 
   if (!view()->mainFrame()->toWebLocalFrame()) {
     CHECK(false) << "This function cannot be called if the main frame is not"
                     "a local frame.";
   }
@@ skipping 68 matching lines @@
 
   // The value returned by std::string::length() may not correspond to the
   // actual number of encoded characters in sequences of multi-byte or
   // variable-length characters.
   blink::WebString newText = blink::WebString::fromUTF8(text);
   size_t textLength = newText.length();
 
   std::vector<blink::WebCompositionUnderline> underlines;
   underlines.push_back(blink::WebCompositionUnderline(
       0, textLength, SK_ColorBLACK, false, SK_ColorTRANSPARENT));
-  inputMethodController()->setComposition(
-      newText, blink::WebVector<blink::WebCompositionUnderline>(underlines),
-      textLength, textLength);
+  if (auto* controller = GetInputMethodController()) {
+    controller->setComposition(
+        newText, blink::WebVector<blink::WebCompositionUnderline>(underlines),
+        textLength, textLength);
+  }
 }
 
 void TextInputController::ForceTextInputStateUpdate() {
   web_view_test_proxy_base_->delegate()->ForceTextInputStateUpdate(
       view()->mainFrame());
 }
 
 blink::WebView* TextInputController::view() {
   return web_view_test_proxy_base_->web_view();
 }
 
-blink::WebInputMethodController* TextInputController::inputMethodController() {
+blink::WebInputMethodController*
+TextInputController::GetInputMethodController() {
+  if (!view()->mainFrame())
+    return nullptr;
+
   blink::WebLocalFrame* mainFrame = view()->mainFrame()->toWebLocalFrame();
   if (!mainFrame) {
     CHECK(false) << "WebView does not have a local main frame and"
                     " cannot handle input method controller tasks.";
   }
   return mainFrame->frameWidget()->getActiveWebInputMethodController();
 }
 
 }  // namespace test_runner