iPhone6以前の端末だとiOSのAdMobでクラッシュする

# 概要
`iPhone6`とか`iPad Mini 4`などの古い端末でAdMob導入後クラッシュが増えてしまう。

# 原因
AdMobで利用してるWebViewがUIWebViewが優先されてしまっているよう。

# 解決方法
UIWebViewではなく、WKWebViewを優先的に使うようにInfo.plistで指定してあげる。

![スクリーンショット 2019-06-11 17.48.33.png](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/30928/3979d337-c25e-8d3b-af8b-ef9bcc8df617.png)


https://groups.google.com/forum/#!topic/google-admob-ads-sdk/ObUaa8gdtA0

# クラッシュログ
```
Crashed: WebThread
0  libGPUSupportMercury.dylib     0x20e6e6f28 gpus_ReturnNotPermittedKillClient
1  AGXGLDriver                    0x212ecc8e0 (Missing)
2  libGPUSupportMercury.dylib     0x20e6e7f04 gpusSubmitDataBuffers
3  AGXGLDriver                    0x212ecde28 (Missing)
4  WebCore                        0x1fa49adf0 WebCore::GraphicsContext3D::presentRenderbuffer() + 104
5  WebCore                        0x1fa0b7c68 -[WebGLLayer display] + 36
6  QuartzCore                     0x1f5cc9668 CA::Context::commit_transaction(CA::Transaction*) + 548
7  QuartzCore                     0x1f5cf7ec8 CA::Transaction::commit() + 608
8  QuartzCore                     0x1f5cf8d30 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 92
9  CoreFoundation                 0x1f16f96bc __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
10 CoreFoundation                 0x1f16f4350 __CFRunLoopDoObservers + 412
11 CoreFoundation                 0x1f16f48f0 __CFRunLoopRun + 1264
12 CoreFoundation                 0x1f16f40e0 CFRunLoopRunSpecific + 436
13 WebCore                        0x1fa5653e8 RunWebThread(void*) + 592
14 libsystem_pthread.dylib        0x1f138425c _pthread_body + 128
15 libsystem_pthread.dylib        0x1f13841bc _pthread_start + 48
16 libsystem_pthread.dylib        0x1f1387cf4 thread_start + 4
```

```
Crashed: WebThread
0  libGPUSupportMercury.dylib     0x219082f28 gpus_ReturnNotPermittedKillClient
1  AGXGLDriver                    0x21d8688e0 (Missing)
2  libGPUSupportMercury.dylib     0x219083f04 gpusSubmitDataBuffers
3  AGXGLDriver                    0x21d869e28 (Missing)
4  libGPUSupportMercury.dylib     0x21908836c gldFlushObject
5  GLEngine                       0x21eb0e748 gleEvaluateTextureImageChange
6  GLEngine                       0x21ea6e9ec glTexImage2D_Exec
7  OpenGLES                       0x1ff42e730 glTexImage2D + 108
8  WebCore                        0x205cab094 WebCore::GraphicsContext3D::texImage2DDirect(unsigned int, int, unsigned int, int, int, int, unsigned int, unsigned int, void const*) + 116
9  WebCore                        0x205caafc0 WebCore::GraphicsContext3D::texImage2D(unsigned int, int, unsigned int, int, int, int, unsigned int, unsigned int, void const*) + 380
10 WebCore                        0x20611ff70 WebCore::WebGLRenderingContextBase::texImage2DBase(unsigned int, int, unsigned int, int, int, int, unsigned int, unsigned int, void const*) + 152
11 WebCore                        0x206120998 WebCore::WebGLRenderingContextBase::texImage2D(unsigned int, int, unsigned int, int, int, int, unsigned int, unsigned int, WTF::RefPtr<JSC::ArrayBufferView, WTF::DumbPtrTraits<JSC::ArrayBufferView> >&&) + 668
12 WebCore                        0x205198604 WebCore::jsWebGLRenderingContextPrototypeFunctionTexImage2D(JSC::ExecState*) + 1444
13 JavaScriptCore                 0x20346c814 llint_entry + 32692
14 JavaScriptCore                 0x20346c200 llint_entry + 31136
15 JavaScriptCore                 0x20346bd34 llint_entry + 29908
16 JavaScriptCore                 0x20346bd34 llint_entry + 29908
17 JavaScriptCore                 0x20346bd34 llint_entry + 29908
18 JavaScriptCore                 0x20346bd34 llint_entry + 29908
19 JavaScriptCore                 0x20346bd9c llint_entry + 30012
20 JavaScriptCore                 0x20346bd34 llint_entry + 29908
21 JavaScriptCore                 0x20346bd34 llint_entry + 29908
22 JavaScriptCore                 0x20346bd34 llint_entry + 29908
23 JavaScriptCore                 0x20346bd34 llint_entry + 29908
24 JavaScriptCore                 0x20346bd34 llint_entry + 29908
25 JavaScriptCore                 0x20346bd34 llint_entry + 29908
26 JavaScriptCore                 0x203464664 vmEntryToJavaScript + 308
27 JavaScriptCore                 0x203ad3840 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) + 424
28 JavaScriptCore                 0x203c8ae94 JSC::profiledCall(JSC::ExecState*, JSC::ProfilingReason, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&, WTF::NakedPtr<JSC::Exception>&) + 200
29 WebCore                        0x20545d3ec WebCore::JSCallbackData::invokeCallback(WebCore::JSDOMGlobalObject&, JSC::JSObject*, JSC::JSValue, JSC::MarkedArgumentBuffer&, WebCore::JSCallbackData::CallbackType, JSC::PropertyName, WTF::NakedPtr<JSC::Exception>&) + 408
30 WebCore                        0x2050231a4 WebCore::JSRequestAnimationFrameCallback::handleEvent(double) + 416
31 WebCore                        0x205726380 WebCore::ScriptedAnimationController::serviceScriptedAnimations(double) + 472
32 WebCore                        0x205bb002c WebCore::ThreadTimers::sharedTimerFiredInternal() + 352
33 WebCore                        0x205bf4a54 WebCore::timerFired(__CFRunLoopTimer*, void*) + 28
34 CoreFoundation                 0x1fc0ad828 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 28
35 CoreFoundation                 0x1fc0ad558 __CFRunLoopDoTimer + 864
36 CoreFoundation                 0x1fc0acd8c __CFRunLoopDoTimers + 248
37 CoreFoundation                 0x1fc0a7c68 __CFRunLoopRun + 1880
38 CoreFoundation                 0x1fc0a71f0 CFRunLoopRunSpecific + 436
39 WebCore                        0x204f16eec RunWebThread(void*) + 592
40 libsystem_pthread.dylib        0x1fbd3825c _pthread_body + 128
41 libsystem_pthread.dylib        0x1fbd381bc _pthread_start + 48
42 libsystem_pthread.dylib        0x1fbd3bcf4 thread_start + 4
```

```
Crashed: WebThread
0  libGPUSupportMercury.dylib     0x20e6e6f28 gpus_ReturnNotPermittedKillClient
1  AGXGLDriver                    0x212ecc8e0 (Missing)
2  libGPUSupportMercury.dylib     0x20e6e7f04 gpusSubmitDataBuffers
3  AGXGLDriver                    0x212ecde28 (Missing)
4  WebCore                        0x1fa49adf0 WebCore::GraphicsContext3D::presentRenderbuffer() + 104
5  WebCore                        0x1fa0b7c68 -[WebGLLayer display] + 36
6  QuartzCore                     0x1f5cc9668 CA::Context::commit_transaction(CA::Transaction*) + 548
7  QuartzCore                     0x1f5cf7ec8 CA::Transaction::commit() + 608
8  QuartzCore                     0x1f5cf8d30 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 92
9  CoreFoundation                 0x1f16f96bc __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
10 CoreFoundation                 0x1f16f4350 __CFRunLoopDoObservers + 412
11 CoreFoundation                 0x1f16f48f0 __CFRunLoopRun + 1264
12 CoreFoundation                 0x1f16f40e0 CFRunLoopRunSpecific + 436
13 WebCore                        0x1fa5653e8 RunWebThread(void*) + 592
14 libsystem_pthread.dylib        0x1f138425c _pthread_body + 128
15 libsystem_pthread.dylib        0x1f13841bc _pthread_start + 48
16 libsystem_pthread.dylib        0x1f1387cf4 thread_start + 4
```