Correct extension directives placement

[digish]

Extension directives must occur before any non-preprocessor tokens.
this will solve shader compilation errors from below generated shader

7-17 03:56:00.100 12331 12609 D skia : GLSL:
07-17 03:56:00.100 12331 12609 D skia : 1 #version 100
07-17 03:56:00.100 12331 12609 D skia : 2
07-17 03:56:00.100 12331 12609 D skia : 3 varying highp vec4 sk_FragCoord_Workaround;
07-17 03:56:00.100 12331 12609 D skia : 4 #extension GL_OES_standard_derivatives : require
07-17 03:56:00.100 12331 12609 D skia : 5 precision mediump float;
07-17 03:56:00.100 12331 12609 D skia : 6 varying mediump vec4 vQuadEdge_Stage0;
07-17 03:56:00.100 12331 12609 D skia : 7 varying mediump vec4 vinColor_Stage0;
07-17 03:56:00.100 12331 12609 D skia : 8 void main() {
07-17 03:56:00.100 12331 12609 D skia : 9 mediump vec4 outputColor_Stage0;
07-17 03:56:00.100 12331 12609 D skia : 10 mediump vec4 outputCoverage_Stage0;
07-17 03:56:00.100 12331 12609 D skia : 11 {
:

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[digish]

I signed it!

…

On Wed, Jul 18, 2018 at 9:19 AM, googlebot ***@***.***> wrote: Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA). 📝 *Please visit https://cla.developers.google.com/ <https://cla.developers.google.com/> to sign.* Once you've signed (or fixed any issues), please reply here (e.g. I signed it!) and we'll verify it. ------------------------------ What to do if you already signed the CLA Individual signers - It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data <https://cla.developers.google.com/clas> and verify that your email is set on your git commits <https://help.github.com/articles/setting-your-email-in-git/>. Corporate signers - Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version <https://opensource.google.com/docs/cla/#troubleshoot>). - The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data <https://cla.developers.google.com/clas> and verify that your email is set on your git commits <https://help.github.com/articles/setting-your-email-in-git/>. - The email used to register you as an authorized contributor must also be attached to your GitHub account <https://github.com/settings/emails>. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#21 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAaqfBLyErbnYGrHW4rIwgeom-DalrAKks5uHrA9gaJpZM4VT5pa> .

-- Digish K Pandya

[rmistry]

Closing old PRs with merge conflicts