Problem:  webGL sites are displayed in the wrong color (usually blue-ish)

Solution: Problem is with skia once again. Output of webgl seems endian-correct, but skia only

          knows how to deal with little endian.

          So we swizzle the output of webgl after reading it from readpixels()

Note:     This does not fix all webGL sites, but is a step in the right direction

diff -r 6b017d3e9733 gfx/gl/GLContext.h

--- a/gfx/gl/GLContext.h    Mon Sep 09 10:04:05 2019 +0200

+++ b/gfx/gl/GLContext.h    Wed Nov 13 17:13:04 2019 +0100

@@ -1551,6 +1551,13 @@

     BEFORE_GL_CALL;

     mSymbols.fReadPixels(x, y, width, height, format, type, pixels);

     OnSyncCall();

+#if MOZ_BIG_ENDIAN

+    uint8_t* itr = (uint8_t*)pixels;

+    for (GLsizei i = 0; i < width * height; i++) {

+      NativeEndian::swapToLittleEndianInPlace((uint32_t*)itr, 1);

+      itr += 4;

+    }

+#endif

     AFTER_GL_CALL;

     mHeavyGLCallsSinceLastFlush = true;

   }