Remove CWV class and move setting User Agent to CWVWebViewConfiguration.

ios/web_view/internal/cwv_web_view.mm

Index: ios/web_view/internal/cwv_web_view.mm
diff --git a/ios/web_view/internal/cwv_web_view.mm b/ios/web_view/internal/cwv_web_view.mm
index 1e199da2baa2178a3c6b38842f95918570f978df..a29d623d9d2bc1d9f2321e5f95f3831bf8fbaff7 100644
--- a/ios/web_view/internal/cwv_web_view.mm
+++ b/ios/web_view/internal/cwv_web_view.mm
@@ -39,7 +39,6 @@ NSString* const kSessionStorageKey = @"sessionStorage";
 }
 
 @interface CWVWebView ()<CRWWebStateDelegate, CRWWebStateObserver> {
-  CWVWebViewConfiguration* _configuration;
   std::unique_ptr<web::WebState> _webState;
   std::unique_ptr<web::WebStateDelegateBridge> _webStateDelegate;
   std::unique_ptr<web::WebStateObserverBridge> _webStateObserver;
@@ -51,12 +50,16 @@ NSString* const kSessionStorageKey = @"sessionStorage";
       _javaScriptDialogPresenter;
 }
 
+// Redefine the property as readwrite.
+@property(nonatomic, copy) CWVWebViewConfiguration* configuration;
 // Redefine the property as readwrite to define -setEstimatedProgress:, which
 // can be used to send KVO notification.
 @property(nonatomic, readwrite) double estimatedProgress;
 
 @end
 
+static NSString* gUserAgentProduct = nil;
+
 @implementation CWVWebView
 
 @synthesize configuration = _configuration;
@@ -65,6 +68,14 @@ NSString* const kSessionStorageKey = @"sessionStorage";
 @synthesize estimatedProgress = _estimatedProgress;
 @synthesize UIDelegate = _UIDelegate;
 
++ (NSString*)userAgentProduct {
+  return gUserAgentProduct;
+}
+
++ (void)setUserAgentProduct:(NSString*)product {
+  gUserAgentProduct = [product copy];
+}
+
 - (instancetype)initWithFrame:(CGRect)frame
                 configuration:(CWVWebViewConfiguration*)configuration {
   self = [super initWithFrame:frame];