Initial version of external_oes texture support and unit test

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 28401fe9e683c26023d9a4d3135619b2c31c018e..a768b371059fbc776c8fee9a17c8dc1d73788ffb 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -46,6 +46,7 @@ GrGLCaps::GrGLCaps(const GrContextOptions& contextOptions,
     fUseNonVBOVertexAndIndexDynamicData = false;
     fIsCoreProfile = false;
     fBindFragDataLocationSupport = false;
+    fExternalTextureSupport = false;
     fSRGBWriteControl = false;
     fRGBA8888PixelsOpsAreSlow = false;
     fPartialFBOReadIsSlow = false;
@@ -259,6 +260,16 @@ void GrGLCaps::init(const GrContextOptions& contextOptions,
     fBindUniformLocationSupport = false;
 #endif
 
+    if (ctxInfo.hasExtension("GL_OES_EGL_image_external")) {
+        if (ctxInfo.glslGeneration() == k110_GrGLSLGeneration) {
+            fExternalTextureSupport = true;
+        } else if (ctxInfo.hasExtension("GL_OES_EGL_image_external_essl3") ||
+                   ctxInfo.hasExtension("OES_EGL_image_external_essl3")) {
+            // At least one driver has been found that has this extension without the "GL_" prefix.
+            fExternalTextureSupport = true;
+        }
+    }
+
 #ifdef SK_BUILD_FOR_WIN
     // We're assuming that on Windows Chromium we're using ANGLE.
     bool isANGLE = kANGLE_GrGLDriver == ctxInfo.driver() ||
@@ -588,13 +599,21 @@ void GrGLCaps::initGLSL(const GrGLContextInfo& ctxInfo) {
         glslCaps->fSecondaryOutputExtensionString = "GL_EXT_blend_func_extended";
     }
 
+    if (fExternalTextureSupport) {
+        if (ctxInfo.glslGeneration() == k110_GrGLSLGeneration) {
+            glslCaps->fExternalTextureExtensionString = "GL_OES_EGL_image_external";
+        } else {
+            glslCaps->fExternalTextureExtensionString = "GL_OES_EGL_image_external_essl3";
+        }
+    }
+
     // The Tegra3 compiler will sometimes never return if we have min(abs(x), 1.0), so we must do
     // the abs first in a separate expression.
     if (kTegra3_GrGLRenderer == ctxInfo.renderer()) {
         glslCaps->fCanUseMinAndAbsTogether = false;
     }
 
-    // On Intel GPU there is an issue where it reads the second arguement to atan "- %s.x" as an int
+    // On Intel GPU there is an issue where it reads the second argument to atan "- %s.x" as an int
     // thus must us -1.0 * %s.x to work correctly
     if (kIntel_GrGLVendor == ctxInfo.vendor()) {
         glslCaps->fMustForceNegatedAtanParamToFloat = true;