Touch up layout of parent permission dialog

Also improved some comments and renamed the following to clarify
their purposes:

section_container -> install_permissions_section_container
ParentPermissionSecton -> ParentPermissionInputSection

Finally, moved install_permissions_section_container and its enclosing
scroll view into the scope of the code that adds extension permissions
view.  This removed dead space created by the scroll view in the case
there were no permissions to display.

Bug: 1052097
Change-Id: I1393d732504c82d586705257f1c1b125640db5d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2134911
Commit-Queue: Dan S <danan@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756407}

chrome/app/generated_resources.grd

@@ -4466,6 +4466,9 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_PARENT_PERMISSION_PROMPT_SELECT_PARENT_LABEL" desc="Text for the label shown above the parent selector.">
         Choose parent account for approval
       </message>
+      <message name="IDS_PARENT_PERMISSION_PROMPT_PARENT_ACCOUNT_LABEL" desc="Text for the label shown above a single parent account email.">
+        Parent account
+      </message>
       <message name="IDS_PARENT_PERMISSION_PROMPT_ENTER_PASSWORD_LABEL" desc="Text for the label shown above the parent password entry field.">
         Enter password
       </message>

chrome/browser/ui/views/parent_permission_dialog_view.h

@@ -34,7 +34,7 @@ namespace views {
 class Label;
 }
 
-class ParentPermissionSection;
+class ParentPermissionInputSection;
 
 // Modal dialog that shows a dialog that prompts a parent for permission by
 // asking them to enter their google account credentials.  This is created only
@@ -156,8 +156,9 @@ class ParentPermissionDialogView : public views::BubbleDialogDelegateView,
 
   bool reprompt_after_incorrect_credential_ = true;
 
-  // Contains the parent-permission related views widgets.
-  std::unique_ptr<ParentPermissionSection> parent_permission_section_;
+  // Contains the parent-permission-input related views widgets.
+  std::unique_ptr<ParentPermissionInputSection>
+      parent_permission_input_section_;
 
   views::Label* invalid_credential_label_ = nullptr;