[ios] Added web// public API to let embedder observe loading progress.

ios/web/web_state/web_state_impl_unittest.mm

Index: ios/web/web_state/web_state_impl_unittest.mm
diff --git a/ios/web/web_state/web_state_impl_unittest.mm b/ios/web/web_state/web_state_impl_unittest.mm
index 2502cb917dc0755e569e35837e4a8f5d5429891e..a47a626c817b5c74d9195c9ec61f3e214df3bd10 100644
--- a/ios/web/web_state/web_state_impl_unittest.mm
+++ b/ios/web/web_state/web_state_impl_unittest.mm
@@ -14,6 +14,7 @@
 #include "ios/web/public/load_committed_details.h"
 #include "ios/web/public/test/test_browser_state.h"
 #include "ios/web/public/web_state/global_web_state_observer.h"
+#include "ios/web/public/web_state/web_state_delegate.h"
 #include "ios/web/public/web_state/web_state_observer.h"
 #include "ios/web/public/web_state/web_state_policy_decider.h"
 #import "ios/web/test/web_test.h"
@@ -106,6 +107,27 @@ class TestGlobalWebStateObserver : public GlobalWebStateObserver {
   bool web_state_destroyed_called_;
 };
 
+// Test delegate to check that the WebStateDelegate methods are called as
+// expected.
+class TestWebStateDelegate : public WebStateDelegate {
+ public:
+  TestWebStateDelegate() : load_progress_changed_called_(false) {}
+
+  // Methods returning true if the corresponding WebStateObserver method has
+  // been called.
+  bool load_progress_changed_called() const {
+    return load_progress_changed_called_;
+  }
+
+ private:
+  // WebStateObserver implementation:
+  void LoadProgressChanged(WebState* source, double progress) override {
+    load_progress_changed_called_ = true;
+  }
+
+  bool load_progress_changed_called_;
+};
+
 // Test observer to check that the WebStateObserver methods are called as
 // expected.
 class TestWebStateObserver : public WebStateObserver {
@@ -344,6 +366,17 @@ TEST_F(WebStateTest, ObserverTest) {
   EXPECT_EQ(nullptr, observer->web_state());
 }
 
+// Tests that WebStateDelegate methods appropriately called.
+TEST_F(WebStateTest, DelegateTest) {
+  TestWebStateDelegate delegate;
+  web_state_->SetDelegate(&delegate);
+
+  // Test that LoadProgressChanged() is called.
+  EXPECT_FALSE(delegate.load_progress_changed_called());
+  web_state_->SendChangeLoadProgress(0.0);
+  EXPECT_TRUE(delegate.load_progress_changed_called());
+}
+
 // Verifies that GlobalWebStateObservers are called when expected.
 TEST_F(WebStateTest, GlobalObserverTest) {
   std::unique_ptr<TestGlobalWebStateObserver> observer(