Fix some dead links in docs

Fix typo and relative path of each links.

Replace chromoting_build_instructions.md with
old_chromoting_build_instructions.md in
docs/chromoting_android_hacking.md
It was renamed in https://codereview.chromium.org/2526563003

Bug: N/A
Change-Id: Ic6b0a297d66c398131a92563be59d826406b41f4
Reviewed-on: https://chromium-review.googlesource.com/1065956
Reviewed-by: Ned Nguyen <[email protected]>
Reviewed-by: Erik Chen <[email protected]>
Reviewed-by: Demetrios Papadopoulos <[email protected]>
Reviewed-by: Albert J. Wong <[email protected]>
Commit-Queue: Albert J. Wong <[email protected]>
Cr-Commit-Position: refs/heads/master@{#560398}
diff --git a/docs/webui_explainer.md b/docs/webui_explainer.md
index b9bb5a7..72507c0 100644
--- a/docs/webui_explainer.md
+++ b/docs/webui_explainer.md
@@ -655,7 +655,7 @@
 
 ## See also
 
-* WebUI's C++ code follows the [Chromium C++ styleguide](../c++/c++.md).
+* WebUI's C++ code follows the [Chromium C++ styleguide](../styleguide/c++/c++.md).
 * WebUI's HTML/CSS/JS code follows the [Chromium Web
   Development Style Guide](../styleguide/web/web.md)