Fix import of trace event files where B/E events' args don't match (#321)

In #273, I changed `CallTreeProfileBuilder.leaveFrame` to fail hard when you request to leave a frame different from the one at the top of the stack. It turns out we were intentionally doing this for trace event imports, because `args` are part of the frame key, and we want to allow profiles to be imported where the `"B"` and `"E"` events have differing `args` field.

This PR fixes the import code to permissively allow the `"args"` field to not match between the `"B"` and `"E"` fields.

**A note on intentional differences between speedscope and chrome://tracing**

`chrome://tracing` will close whichever frame is at the top when it gets an `"E"` event, regardless of whether the name or the args match. speedscope will ignore the event entirely if the `"name"` field doesn't match, but will warn but still close the frame if the `"name"`s match but the `"args"` don't.
```
[
  {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
  {"pid": 0, "tid": 0, "ph": "B", "name": "beta", "ts": 1},
  {"pid": 0, "tid": 0, "ph": "E", "name": "gamma", "ts": 2},
  {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 9},
  {"pid": 0, "tid": 0, "ph": "E", "name": "alpha", "ts": 10}
]
```
### speedscope
![image](https://user-images.githubusercontent.com/150329/97098205-7365dd00-1637-11eb-9869-4e81ebebcee1.png)
```
warning: ts=2: Request to end "gamma" when "beta" was on the top of the stack. Doing nothing instead.
```
### chrome://tracing
![image](https://user-images.githubusercontent.com/150329/97098215-87114380-1637-11eb-909c-b2e70c7291a4.png)

sample/profiles/trace-event/end-event-with-empty-stack.json

@@ -0,0 +1,5 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "alpha", "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 2}
+]

sample/profiles/trace-event/end-non-top-of-stack.json

@@ -0,0 +1,6 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 1}, "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "B", "args": {"x": 2}, "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "A", "args": {"x": 2}, "ts": 10},
+  {"pid": 0, "tid": 0, "ph": "X", "name": "Z", "args": {"x": 1}, "ts": 10, "dur": 1}
+]

sample/profiles/trace-event/mismatched-args.json

@@ -0,0 +1,4 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 1}, "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "A", "args": {"x": 2}, "ts": 10}
+]

sample/profiles/trace-event/mismatched-name.json

@@ -0,0 +1,4 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 10}
+]

sample/profiles/trace-event/not-enough-end-events.json

@@ -0,0 +1,5 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 1}, "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 2}, "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "X", "name": "A", "args": {"x": 1}, "ts": 10, "dur": 1}
+]

sample/profiles/trace-event/only-begin-events.json

@@ -0,0 +1,5 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 1}, "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "B", "args": {"x": 2}, "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "C", "args": {"x": 2}, "ts": 2}
+]

sample/profiles/trace-event/out-of-order-unbalanced-name.json

@@ -0,0 +1,6 @@
+[
+  {"pid": 0, "tid": 0, "ph": "E", "name": "alpha", "ts": 9},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 10},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "beta", "ts": 1}
+]

sample/profiles/trace-event/out-of-order.json

@@ -0,0 +1,10 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "B", "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "B", "ts": 9},
+
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "A", "ts": 10},
+
+  {"pid": 0, "tid": 0, "ph": "B", "name": "C", "ts": 2},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "C", "ts": 8}
+]

sample/profiles/trace-event/unbalanced-args.json

@@ -0,0 +1,6 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 1}, "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "args": {"x": 2}, "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "A", "args": {"x": 1}, "ts": 9},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "A", "args": {"x": 2}, "ts": 10}
+]

sample/profiles/trace-event/unbalanced-name.json

@@ -0,0 +1,6 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "alpha", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "beta", "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "alpha", "ts": 9},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "beta", "ts": 10}
+]

sample/profiles/trace-event/zero-duration-events.json

@@ -0,0 +1,9 @@
+[
+  {"pid": 0, "tid": 0, "ph": "B", "name": "A", "ts": 0},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "B", "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "B", "ts": 1},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "C", "ts": 2},
+  {"pid": 0, "tid": 0, "ph": "B", "name": "C", "ts": 2},
+  {"pid": 0, "tid": 0, "ph": "X", "name": "D", "ts": 3, "dur": 0},
+  {"pid": 0, "tid": 0, "ph": "E", "name": "A", "ts": 10}
+]