always set the initial-scale

Conversation view's design implies that the page-scale is always 1.0,
since zooming out is done on a per-message basis.

Legacy WebView defaulted to this, but Chromium WebView needs it set
explicitly.

Bug: 10372999
Change-Id: I586557e6c3aac56ea95938697f2ad0640dab002b
diff --git a/res/raw/template_conversation_upper.html b/res/raw/template_conversation_upper.html
index cd448e3..5ba3a84 100644
--- a/res/raw/template_conversation_upper.html
+++ b/res/raw/template_conversation_upper.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <html>
 <head>
-  <meta id="meta-viewport" name="viewport" content="width=device-width"
+  <meta id="meta-viewport" name="viewport" content="width=device-width initial-scale=1.0"
       data-zoom-on="maximum-scale=2" data-zoom-off="user-scalable=no" />
   <style>
     .elided-text,