Refactor web shell integration tests utilities.

ios/web/shell/test/earl_grey/shell_matchers.h

Index: ios/web/shell/test/earl_grey/shell_matchers.h
diff --git a/ios/web/shell/test/shell_matchers.h b/ios/web/shell/test/earl_grey/shell_matchers.h
similarity index 77%
rename from ios/web/shell/test/shell_matchers.h
rename to ios/web/shell/test/earl_grey/shell_matchers.h
index 2405d8d3f6aa33afc8474f14b332ddae8a689ab7..2cd70a9616a35c4bb7c161d4f438ba7e023cbeb0 100644
--- a/ios/web/shell/test/shell_matchers.h
+++ b/ios/web/shell/test/earl_grey/shell_matchers.h
@@ -6,6 +6,9 @@
 
 namespace web {
 
+// Shorthand for GREYMatchers::matcherForWebViewContainingText.
+id<GREYMatcher> webViewContainingText(NSString* text);
+
 // Shorthand for GREYMatchers::matcherForBackButton.
 id<GREYMatcher> backButton();
 
@@ -19,6 +22,9 @@ id<GREYMatcher> addressField();
 
 @interface GREYMatchers (WebShellAdditions)
 
+// Matcher for WKWebView containing |text|.
++ (id<GREYMatcher>)matcherForWebViewContainingText:(NSString*)text;
+
 // Matcher for back button in web shell.
 + (id<GREYMatcher>)matcherForWebShellBackButton;