[unseasoned-pdf] Fix nits in PdfViewWebPluginTest.ChangeTextSelection.

Following up on https://crrev.com/c/2889914/ regarding test
PdfViewWebPluginTest.ChangeTextSelection:

- Replace the custom matcher EqualsWebString() with
  blink::WebString::FromUTF8().

- Remove the InSequence variable since there is no need to keep
  EXPECT_CALL() calls in order.

- Remove an extra header.

Bug: 1199558
Change-Id: Id829588f2d9cc7572e492219267fd2d9ae770853
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2898153
Commit-Queue: Hui Yingst <nigi@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#883181}

pdf/pdf_view_web_plugin_unittest.cc

@@ -5,7 +5,6 @@
 #include "pdf/pdf_view_web_plugin.h"
 
 #include <memory>
-#include <string>
 #include <utility>
 
 #include "cc/paint/paint_canvas.h"
@@ -69,10 +68,6 @@ SkBitmap GenerateExpectedBitmapForPaint(float device_scale,
   return expected_bitmap;
 }
 
-MATCHER_P(EqualsWebString, selected_string, "") {
-  return arg.Utf8() == selected_string;
-}
-
 class FakeContainerWrapper final : public PdfViewWebPlugin::ContainerWrapper {
  public:
   explicit FakeContainerWrapper(PdfViewWebPlugin* web_plugin)
@@ -293,10 +288,9 @@ TEST_F(PdfViewWebPluginTest, ChangeTextSelection) {
   ASSERT_TRUE(plugin_->SelectionAsText().IsEmpty());
   ASSERT_TRUE(plugin_->SelectionAsMarkup().IsEmpty());
 
-  testing::InSequence s;
   static constexpr char kSelectedText[] = "1234";
   EXPECT_CALL(*wrapper_ptr_,
-              TextSelectionChanged(EqualsWebString(kSelectedText), 0,
+              TextSelectionChanged(blink::WebString::FromUTF8(kSelectedText), 0,
                                    gfx::Range(0, 4)));
 
   plugin_->SetSelectedText(kSelectedText);
@@ -305,8 +299,9 @@ TEST_F(PdfViewWebPluginTest, ChangeTextSelection) {
   EXPECT_EQ(kSelectedText, plugin_->SelectionAsMarkup().Utf8());
 
   static constexpr char kEmptyText[] = "";
-  EXPECT_CALL(*wrapper_ptr_, TextSelectionChanged(EqualsWebString(kEmptyText),
-                                                  0, gfx::Range(0, 0)));
+  EXPECT_CALL(*wrapper_ptr_,
+              TextSelectionChanged(blink::WebString::FromUTF8(kEmptyText), 0,
+                                   gfx::Range(0, 0)));
   plugin_->SetSelectedText(kEmptyText);
   EXPECT_FALSE(plugin_->HasSelection());
   EXPECT_TRUE(plugin_->SelectionAsText().IsEmpty());