[WebGL] rendering is broken (only a part of the screen is fine, the rest is visual garbage).
In Unity 5.5.1p4 the issue has evolved: before that the issue was only noticeable running the project in Fullscreen mode.

Steps to reproduce:
1. Extract the ProjectUnityBugFullScreenWebGL.7z file to the desktop.
2. Right click on the folder and choose Properties.
3. Open the Security tab and click Edit to Edit the permissions.
4. Add a user then type in IIS_IUSRS and IUSR into the “Enter the object names to select” text box.
5. Click OK.
6. Open the project in Unity 5.5.0p1 and build the asset bundle and viewer server (release).
7. Install Microsoft IIS.
8. Set up 2 servers: an assetsBundlesServer and a viewerServer (make sure the websites point to the folder with the web.config in it).
- Make sure the websites are your IP address + a port number (different port numbers for each) (use IP address)
- For example: Viewer Server - 192.168.1.1:80, Asset Bundle Server - 192.168.1.1:81
9. Navigate to ProjectUnityBugFullScreenWebGL\Assets\Scripts\Core\AssetLoadingController.cs and open it.
10. Change the Asset Bundle Server path on line 9 to your Asset Bundle Server.
- For example: “http://192.168.1.1:81/assets/WebGL/”
11. Open the web.config file in ProjectUnityBugFullScreenWebGL/PortfolioViewerServers/ViewerServer. (If web.config does not exist, create it by yourself).
12. Delete everything in the file and paste:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<staticContent>
<mimeMap fileExtension=".obj" mimeType="application/obj" />
<mimeMap fileExtension=".mtl" mimeType="application/mtl" />
<mimeMap fileExtension=".dds" mimeType="application/dds" />
<mimeMap fileExtension=".fbx" mimeType="application/fbx" />

<mimeMap fileExtension=".mem" mimeType="application/octet-stream" />
<mimeMap fileExtension=".data" mimeType="application/octet-stream" />
<mimeMap fileExtension=".memgz" mimeType="application/octet-stream"/>
<mimeMap fileExtension=".datagz" mimeType="application/octet-stream"/>
<mimeMap fileExtension=".unity3dgz" mimeType="application/octet-stream" />
<mimeMap fileExtension=".jsgz" mimeType="application/x-javascript; charset=UTF-8" />
</staticContent>
<directoryBrowse enabled="true" />
</system.webServer>
</configuration>

13. Save the web.config.
14. Go into Unity again and build the asset bundle and viewer (release).
15. Refresh the websites in IIS and open the viewerServer website in Chrome or any other browser.
16. Once the application loads, press ‘U’ to load an asset then click ‘Red Paint’ on the side to load the substance.
17. Try to zoom-in / move the Red circle using a right mouse button.

Expected behavior: Red circle moves / zooms-in
Actual result: Visual garbage appear

Reproduced with: 5.5.2.p4, 5.5.1p4, 5.5.0p1; Chrome 56.0, Mozilla Firefox 51.0.
Not reproduce with: 5.4.4p4, 5.6.0b10 (can't build WebGL Build because of the errors in the Console).