Revert "Rewrite switch statements in GLSL strict-ES2 mode."

This reverts commit 45e3838006df8bc393fe6f4ca1cff999b41167f4.

Reason for revert: Also need to rewrite them in actual ES2 mode.

Original change's description:
> Rewrite switch statements in GLSL strict-ES2 mode.
>
> Once this lands, switch statements will work everywhere--Metal, SPIR-V,
> GLSL, and SkVM.
>
> Change-Id: I2797d0a872de8be77bb9f7aa6acb93421d571d70
> Bug: skia:12450
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/452356
> Commit-Queue: John Stiles <johnstiles@google.com>
> Auto-Submit: John Stiles <johnstiles@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

Bug: skia:12450
Change-Id: I92656ed40289872405c0873f2c56a52b04e35b1d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/452556
Auto-Submit: Brian Osman <brianosman@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
diff --git a/src/sksl/codegen/SkSLGLSLCodeGenerator.cpp b/src/sksl/codegen/SkSLGLSLCodeGenerator.cpp
index 5c86c94..d4479db 100644
--- a/src/sksl/codegen/SkSLGLSLCodeGenerator.cpp
+++ b/src/sksl/codegen/SkSLGLSLCodeGenerator.cpp
@@ -1355,66 +1355,8 @@
 
 void GLSLCodeGenerator::writeSwitchStatement(const SwitchStatement& s) {
     if (fProgram.fConfig->strictES2Mode()) {
-        String fallthroughVar = "_tmpSwitchFallthrough" + to_string(fVarCount++);
-        String valueVar = "_tmpSwitchValue" + to_string(fVarCount++);
-        String loopVar = "_tmpSwitchLoop" + to_string(fVarCount++);
-        this->write("int ");
-        this->write(valueVar);
-        this->write(" = ");
-        this->writeExpression(*s.value(), Precedence::kAssignment);
-        this->write(", ");
-        this->write(fallthroughVar);
-        this->writeLine(" = 0; ");
-        this->write("for (int ");
-        this->write(loopVar);
-        this->write(" = 0; ");
-        this->write(loopVar);
-        this->write(" < 1; ");
-        this->write(loopVar);
-        this->writeLine("++) {");
-        fIndentation++;
-
-        bool firstCase = true;
-        for (const std::unique_ptr<Statement>& stmt : s.cases()) {
-            const SwitchCase& c = stmt->as<SwitchCase>();
-            if (c.value()) {
-                this->write("if ((");
-                if (firstCase) {
-                    firstCase = false;
-                } else {
-                    this->write(fallthroughVar);
-                    this->write(" > 0) || (");
-                }
-                this->write(valueVar);
-                this->write(" == ");
-                this->writeExpression(*c.value(), Precedence::kEquality);
-                this->writeLine(")) {");
-                fIndentation++;
-
-                // We write the entire case-block statement here, and then set `switchFallthrough`
-                // to 1. If the case-block had a break statement in it, we break out of the outer
-                // for-loop entirely, meaning the `switchFallthrough` assignment never occurs, nor
-                // does any code after it inside the switch. We've forbidden `continue` statements
-                // inside switch case-blocks entirely, so we don't need to consider their effect on
-                // control flow; see the Finalizer in FunctionDefinition::Convert.
-                this->writeStatement(*c.statement());
-                this->finishLine();
-                this->write(fallthroughVar);
-                this->write(" = 1;");
-                this->writeLine();
-
-                fIndentation--;
-                this->writeLine("}");
-            } else {
-                // This is the default case. Since it's always last, we can just dump in the code.
-                this->writeStatement(*c.statement());
-                this->finishLine();
-            }
-        }
-
-        fIndentation--;
-        this->writeLine("}");
-        return;
+        // TODO(skia:12450): write switch compatibility code
+        fContext.fErrors->error(s.fOffset, "switch statements are not supported");
     }
 
     this->write("switch (");